ICSE – Grade 10 – Physics – Ch 03 – QA

Questions & Answers

ICSE - Grade - 10

Subject: Physics

Chapter - 03 - Machines

Types of Questions

MCQ

  1. Which of the following is not a function of a machine?
     a) To act as a force multiplier
     b) To change the direction of effort
     c) To increase energy output
     d) To change the point of application of effort
     Answer: c) To increase energy output


  2. The ratio of load to effort is called:
     a) Velocity ratio
     b) Mechanical advantage
     c) Efficiency
     d) Power ratio
     Answer: b) Mechanical advantage


  3. In the relation η = (MA / VR) × 100%, η represents:
     a) Power
     b) Efficiency
     c) Force ratio
     d) Work input
     Answer: b) Efficiency


  4. For a practical machine, which of the following is true?
     a) MA = VR
     b) MA > VR
     c) MA < VR
     d) MA = 0
     Answer: c) MA < VR


  5. The unit of mechanical advantage is:
     a) Newton
     b) Metre
     c) No unit
     d) Joule
     Answer: c) No unit


  6. In a single fixed pulley, the velocity ratio is:
     a) 1
     b) 2
     c) 3
     d) Equal to MA
     Answer: a) 1


  7. The principle of a lever is based on:
     a) Conservation of energy
     b) Newton’s first law
     c) Moments
     d) Friction
     Answer: c) Moments


  8. In a class II lever, the load is located:
     a) Between fulcrum and effort
     b) Between effort and fulcrum
     c) At the fulcrum
     d) Anywhere on the lever
     Answer: a) Between fulcrum and effort


  9. In a class III lever, mechanical advantage is:
     a) Greater than 1
     b) Equal to 1
     c) Less than 1
     d) Infinite
     Answer: c) Less than 1


  10. An example of a class I lever is:
     a) Wheelbarrow
     b) Crowbar
     c) Human forearm
     d) Nutcracker
     Answer: b) Crowbar


  11. An example of a class II lever is:
     a) Scissors
     b) Nutcracker
     c) Tweezers
     d) Pliers
     Answer: b) Nutcracker


  12. An example of a class III lever is:
     a) Nutcracker
     b) Wheelbarrow
     c) Human forearm
     d) Seesaw
     Answer: c) Human forearm


  13. Velocity ratio is defined as:
     a) Load / Effort
     b) Effort distance / Load distance
     c) Output / Input
     d) Work output / Work input
     Answer: b) Effort distance / Load distance


  14. In a single movable pulley, ideal mechanical advantage is:
     a) 1
     b) 2
     c) 3
     d) Equal to VR
     Answer: b) 2


  15. For an ideal machine, η is:
     a) 0%
     b) 50%
     c) 100%
     d) Less than 1%
     Answer: c) 100%


  16. The load arm in a lever is:
     a) Distance from load to fulcrum
     b) Distance from effort to fulcrum
     c) Distance from load to effort
     d) Always equal to effort arm
     Answer: a) Distance from load to fulcrum


  17. Efficiency of a machine can never be:
     a) Equal to 100%
     b) Greater than 100%
     c) Less than 100%
     d) Zero
     Answer: b) Greater than 100%


  18. In a block and tackle system, VR equals:
     a) Number of pulleys in the upper block
     b) Number of pulleys in the lower block
     c) Total number of supporting strands
     d) Load / Effort
     Answer: c) Total number of supporting strands


  19. The SI unit of effort is:
     a) Joule
     b) Watt
     c) Newton
     d) Metre
     Answer: c) Newton


  20. The work output of a machine is:
     a) Effort × Effort distance
     b) Load × Load distance
     c) MA × VR
     d) η × Input
     Answer: b) Load × Load distance


  21. A single fixed pulley is used mainly to:
     a) Multiply force
     b) Multiply speed
     c) Change direction of effort
     d) Increase efficiency
     Answer: c) Change direction of effort


  22. If a machine has MA = 4 and VR = 5, efficiency is:
     a) 80%
     b) 100%
     c) 20%
     d) 125%
     Answer: a) 80%


  23. The effort arm in a lever is:
     a) Distance from load to fulcrum
     b) Distance from effort to fulcrum
     c) Distance from fulcrum to middle
     d) Equal to load arm
     Answer: b) Distance from effort to fulcrum


  24. The unit of velocity ratio is:
     a) Newton
     b) No unit
     c) Joule
     d) Watt
     Answer: b) No unit


  25. For a speed multiplier machine:
     a) MA > 1
     b) MA = 1
     c) MA < 1
     d) MA = VR
     Answer: c) MA < 1


  26. Which of the following is a speed multiplier?
     a) Wheelbarrow
     b) Nutcracker
     c) Scissors
     d) Crowbar
     Answer: c) Scissors


  27. The relation between work input and output for an ideal machine is:
     a) Input > Output
     b) Input = Output
     c) Input < Output
     d) No relation
     Answer: b) Input = Output


  28. A crowbar is an example of:
     a) Class I lever
     b) Class II lever
     c) Class III lever
     d) None of these
     Answer: a) Class I lever


  29. A wheelbarrow is an example of:
     a) Class I lever
     b) Class II lever
     c) Class III lever
     d) Speed multiplier
     Answer: b) Class II lever


  30. Tweezers are an example of:
     a) Class I lever
     b) Class II lever
     c) Class III lever
     d) Speed multiplier
     Answer: c) Class III lever


  31. In a class II lever, MA is:
     a) Less than 1
     b) Equal to 1
     c) Greater than 1
     d) Negative
     Answer: c) Greater than 1


  32. Which factor reduces efficiency in real machines?
     a) Friction
     b) Low VR
     c) Large effort arm
     d) Large load
     Answer: a) Friction


  33. A pulley having VR = 2 is:
     a) Single fixed
     b) Single movable
     c) Block and tackle with 2 strands
     d) Class I lever
     Answer: b) Single movable


  34. In levers, increasing effort arm:
     a) Decreases MA
     b) Increases MA
     c) No change in MA
     d) Decreases VR
     Answer: b) Increases MA


  35. A nutcracker is an example of:
     a) Class I lever
     b) Class II lever
     c) Class III lever
     d) Speed multiplier
     Answer: b) Class II lever


  36. Efficiency formula in terms of MA and VR is:
     a) η = (VR / MA) × 100%
     b) η = (MA / VR) × 100%
     c) η = MA × VR × 100%
     d) η = (MA − VR) × 100%
     Answer: b) η = (MA / VR) × 100%


  37. If MA = VR, the machine is:
     a) Ideal
     b) Real
     c) Inefficient
     d) Speed multiplier
     Answer: a) Ideal


  38. Which of these levers is used in human body for nodding head?
     a) Class I
     b) Class II
     c) Class III
     d) All of these
     Answer: a) Class I


  39. Standing on toes represents:
     a) Class I lever
     b) Class II lever
     c) Class III lever
     d) Speed multiplier
     Answer: b) Class II lever


  40. Human forearm lifting a weight is:
     a) Class I lever
     b) Class II lever
     c) Class III lever
     d) Speed multiplier
     Answer: c) Class III lever


  41. VR of a block and tackle system with 4 supporting strands is:
     a) 2
     b) 3
     c) 4
     d) 8
     Answer: c) 4


  42. The gain in speed means:
     a) Load moves more than effort
     b) Effort moves more than load
     c) Load = Effort
     d) VR = 1
     Answer: b) Effort moves more than load


  43. For a single movable pulley, VR is:
     a) Equal to MA
     b) Less than MA
     c) Greater than MA in real use
     d) Zero
     Answer: c) Greater than MA in real use


  44. The load in a machine is measured in:
     a) Joules
     b) Watts
     c) Newtons
     d) Metres
     Answer: c) Newtons


  45. The efficiency of an ideal single fixed pulley is:
     a) 50%
     b) 75%
     c) 100%
     d) Less than 100%
     Answer: c) 100%


  46. A lever with effort between load and fulcrum is:
     a) Class I
     b) Class II
     c) Class III
     d) None
     Answer: c) Class III


  47. MA of a single fixed pulley is:
     a) 0.5
     b) 1
     c) 2
     d) Equal to VR
     Answer: b) 1


  48. In an ideal block and tackle with 3 strands, VR is:
     a) 2
     b) 3
     c) 4
     d) 6
     Answer: b) 3


  49. η < 1 for real machines because:
     a) MA > VR
     b) Friction and weight of moving parts
     c) MA = VR
     d) VR = 0
     Answer: b) Friction and weight of moving parts


  50. Which of these is not a type of lever?
     a) Class I
     b) Class II
     c) Class III
     d) Class IV
     Answer: d) Class IV

Fill in the Blanks

  1. A machine is used to make our work _______.
     Answer: easier


  2. The force applied to a machine is called _______.
     Answer: effort


  3. The resistance overcome by a machine is called _______.
     Answer: load


  4. Mechanical advantage is given by the formula MA = _______.
     Answer: Load / Effort


  5. Velocity ratio is the ratio of distance moved by effort to distance moved by _______.
     Answer: load


  6. Efficiency (η) is given by the formula η = (MA / VR) × _______.
     Answer: 100%


  7. In an ideal machine, efficiency is _______%.
     Answer: 100


  8. For a practical machine, MA is always _______ than VR.
     Answer: less


  9. The principle of a lever is based on the principle of _______.
     Answer: moments


  10. The distance from load to fulcrum is called the _______ arm.
     Answer: load


  11. The distance from effort to fulcrum is called the _______ arm.
     Answer: effort


  12. A crowbar is an example of a _______ class lever.
     Answer: first


  13. A nutcracker is an example of a _______ class lever.
     Answer: second


  14. A human forearm lifting a weight is an example of a _______ class lever.
     Answer: third


  15. A wheelbarrow is an example of a _______ class lever.
     Answer: second


  16. In a class I lever, the _______ is between effort and load.
     Answer: fulcrum


  17. In a class II lever, the _______ is between fulcrum and effort.
     Answer: load


  18. In a class III lever, the _______ is between fulcrum and load.
     Answer: effort


  19. The velocity ratio of a single fixed pulley is _______.
     Answer: 1


  20. The velocity ratio of a single movable pulley is ideally _______.
     Answer: 2


  21. A single fixed pulley only changes the _______ of effort.
     Answer: direction


  22. In a block and tackle system, VR equals the number of _______ strands.
     Answer: supporting


  23. The unit of mechanical advantage is _______.
     Answer: no unit


  24. The unit of effort in SI is _______.
     Answer: newton


  25. The unit of load in SI is _______.
     Answer: newton


  26. For a speed multiplier, MA is _______ than 1.
     Answer: less


  27. For a force multiplier, MA is _______ than 1.
     Answer: greater


  28. Scissors are an example of a _______ class lever.
     Answer: first


  29. Tweezers are an example of a _______ class lever.
     Answer: third


  30. Standing on toes is an example of a _______ class lever.
     Answer: second


  31. Nodding the head is an example of a _______ class lever.
     Answer: first


  32. Efficiency is reduced in real machines due to _______ and weight of moving parts.
     Answer: friction


  33. For an ideal single movable pulley, MA = _______.
     Answer: 2


  34. The formula for work output is Load × _______ distance.
     Answer: load


  35. The formula for work input is Effort × _______ distance.
     Answer: effort


  36. If MA = VR, the machine is said to be _______.
     Answer: ideal


  37. The SI unit of efficiency is _______.
     Answer: no unit


  38. In a block and tackle with 3 strands, VR = _______.
     Answer: 3


  39. In a single fixed pulley, MA is ideally _______.
     Answer: 1


  40. Gain in speed means effort moves _______ than load.
     Answer: more


  41. The symbol η is used for _______.
     Answer: efficiency


  42. In the formula η = (MA / VR) × 100%, MA stands for _______.
     Answer: mechanical advantage


  43. In the same formula, VR stands for _______.
     Answer: velocity ratio


  44. The main reason for MA being less than VR in real machines is _______.
     Answer: energy loss due to friction


  45. For a single movable pulley, VR is _______ than MA in practice.
     Answer: greater


  46. The effort arm is measured from the effort to the _______.
     Answer: fulcrum


  47. The load arm is measured from the load to the _______.
     Answer: fulcrum


  48. The MA of a block and tackle equals the number of _______ in the ideal case.
     Answer: supporting strands


  49. VR has _______ units.
     Answer: no


  50. A lever which multiplies speed will have MA _______ than 1.
     Answer: less

Name the Following

  1. The force applied to a machine.
     Answer: Effort


  2. The resistance overcome by a machine.
     Answer: Load


  3. The ratio of load to effort.
     Answer: Mechanical advantage


  4. The ratio of distance moved by effort to distance moved by load.
     Answer: Velocity ratio


  5. The ratio of work output to work input.
     Answer: Efficiency


  6. The distance between load and fulcrum.
     Answer: Load arm


  7. The distance between effort and fulcrum.
     Answer: Effort arm


  8. The principle on which levers work.
     Answer: Principle of moments


  9. The class of lever with fulcrum between effort and load.
     Answer: Class I lever


  10. The class of lever with load between fulcrum and effort.
     Answer: Class II lever


  11. The class of lever with effort between fulcrum and load.
     Answer: Class III lever


  12. The type of machine that changes the direction of effort only.
     Answer: Single fixed pulley


  13. The type of pulley with VR = 2 in ideal case.
     Answer: Single movable pulley


  14. The pulley system with VR equal to the number of supporting strands.
     Answer: Block and tackle system


  15. The type of lever to which a crowbar belongs.
     Answer: Class I lever


  16. The type of lever to which a nutcracker belongs.
     Answer: Class II lever


  17. The type of lever to which a human forearm belongs.
     Answer: Class III lever


  18. The type of lever to which scissors belong.
     Answer: Class I lever


  19. The type of lever to which tweezers belong.
     Answer: Class III lever


  20. The type of lever shown by standing on toes.
     Answer: Class II lever


  21. The type of lever shown by nodding the head.
     Answer: Class I lever


  22. The SI unit of effort.
     Answer: Newton


  23. The SI unit of load.
     Answer: Newton


  24. The SI unit of mechanical advantage.
     Answer: No unit


  25. The SI unit of velocity ratio.
     Answer: No unit


  26. The SI unit of efficiency.
     Answer: No unit


  27. A lever with MA less than 1.
     Answer: Speed multiplier


  28. A lever with MA greater than 1.
     Answer: Force multiplier


  29. The formula for mechanical advantage in levers.
     Answer: Effort arm / Load arm


  30. The formula for efficiency in terms of MA and VR.
     Answer: (MA / VR) × 100%


  31. The term for the work done on the machine.
     Answer: Work input


  32. The term for the work done by the machine.
     Answer: Work output


  33. The factor that reduces efficiency in real machines.
     Answer: Friction


  34. The other factor besides friction that reduces efficiency.
     Answer: Weight of moving parts


  35. A lever in the human body that acts as a class III lever.
     Answer: Human forearm


  36. A class II lever used in daily life for lifting loads.
     Answer: Wheelbarrow


  37. A lever used for cutting paper that is class I.
     Answer: Scissors


  38. A lever used for holding small objects that is class III.
     Answer: Tweezers


  39. A lever used for cracking nuts that is class II.
     Answer: Nutcracker


  40. The fixed point about which a lever rotates.
     Answer: Fulcrum


  41. The pulley type where the axis is fixed in position.
     Answer: Single fixed pulley


  42. The pulley type where the axis moves along with load.
     Answer: Single movable pulley


  43. The block in a block and tackle that is attached to the load.
     Answer: Lower block


  44. The block in a block and tackle that is fixed to a support.
     Answer: Upper block


  45. The number of strands supporting the load in a VR = 4 system.
     Answer: Four


  46. A lever in the human body that acts as a class II lever.
     Answer: Standing on toes


  47. A lever in the human body that acts as a class I lever.
     Answer: Nodding the head


  48. The term for gain in speed in a machine.
     Answer: Speed multiplier effect


  49. The term for gain in force in a machine.
     Answer: Force multiplier effect


  50. The general name for devices like levers and pulleys that make work easier.
     Answer: Simple machines

Answer in One Word

  1. Force applied to a machine.
     Answer: Effort


  2. Resistance overcome by a machine.
     Answer: Load


  3. Ratio of load to effort.
     Answer: Mechanical advantage


  4. Ratio of effort distance to load distance.
     Answer: Velocity ratio


  5. Ratio of work output to work input.
     Answer: Efficiency


  6. Distance from load to fulcrum.
     Answer: Load arm


  7. Distance from effort to fulcrum.
     Answer: Effort arm


  8. Point about which a lever rotates.
     Answer: Fulcrum


  9. Class of lever with fulcrum in middle.
     Answer: First


  10. Class of lever with load in middle.
     Answer: Second


  11. Class of lever with effort in middle.
     Answer: Third


  12. Lever type of crowbar.
     Answer: First


  13. Lever type of nutcracker.
     Answer: Second


  14. Lever type of human forearm.
     Answer: Third


  15. Lever type of scissors.
     Answer: First


  16. Lever type of tweezers.
     Answer: Third


  17. Lever type of wheelbarrow.
     Answer: Second


  18. Lever type when standing on toes.
     Answer: Second


  19. Lever type when nodding head.
     Answer: First


  20. Pulley with VR = 1.
     Answer: Single fixed pulley


  21. Pulley with VR = 2.
     Answer: Single movable pulley


  22. Pulley system with VR equal to number of supporting strands.
     Answer: Block and tackle


  23. SI unit of effort.
     Answer: Newton


  24. SI unit of load.
     Answer: Newton


  25. SI unit of mechanical advantage.
     Answer: None


  26. SI unit of velocity ratio.
     Answer: None


  27. SI unit of efficiency.
     Answer: None


  28. Machine with MA < 1.
     Answer: Speed multiplier


  29. Machine with MA > 1.
     Answer: Force multiplier


  30. Work done on the machine.
     Answer: Input


  31. Work done by the machine.
     Answer: Output


  32. Factor reducing efficiency in real machines.
     Answer: Friction


  33. Other factor reducing efficiency besides friction.
     Answer: Weight


  34. Ideal efficiency percentage.
     Answer: 100


  35. Pulley type with axis fixed to support.
     Answer: Single fixed pulley


  36. Pulley type with axis moving with load.
     Answer: Single movable pulley


  37. Block in block and tackle attached to load.
     Answer: Lower


  38. Block in block and tackle fixed to support.
     Answer: Upper


  39. Number of strands in VR = 4 block and tackle.
     Answer: Four


  40. Formula for efficiency in terms of MA and VR.
     Answer: MA/VR × 100%


  41. Formula for mechanical advantage in levers.
     Answer: Effort arm/Load arm


  42. Unit of work in SI.
     Answer: Joule


  43. Unit of power in SI.
     Answer: Watt


  44. Lever type of pliers.
     Answer: First


  45. Lever type of tongs.
     Answer: Third


  46. Lever type of paper cutter.
     Answer: First


  47. Lever type of bottle opener.
     Answer: Second


  48. Lever type of fishing rod.
     Answer: Third


  49. Term for movement gain in speed multiplier.
     Answer: Speed gain


  50. General name for devices like levers and pulleys.
     Answer: Simple machines

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Find the Odd Man Out

  1. Crowbar, Scissors, Nutcracker, Pliers
     Answer: Nutcracker
     Explanation: Nutcracker is a class II lever; others are class I levers.


  2. Wheelbarrow, Nutcracker, Bottle opener, Tweezers
     Answer: Tweezers
     Explanation: Tweezers are a class III lever; others are class II levers.


  3. Scissors, Crowbar, Seesaw, Wheelbarrow
     Answer: Wheelbarrow
     Explanation: Wheelbarrow is a class II lever; others are class I levers.


  4. Single fixed pulley, Single movable pulley, Block and tackle, Wheelbarrow
     Answer: Wheelbarrow
     Explanation: Wheelbarrow is a lever; others are pulley systems.


  5. Efficiency, Mechanical advantage, Velocity ratio, Power
     Answer: Power
     Explanation: Power is not a basic term of machines in this chapter; others are key machine parameters.


  6. Fulcrum, Load arm, Effort arm, Pulley rope
     Answer: Pulley rope
     Explanation: Pulley rope is part of a pulley system; others are parts of a lever.


  7. MA, VR, η, Joule
     Answer: Joule
     Explanation: Joule is a unit of work; others are dimensionless ratios.


  8. Nodding head, Scissors, Crowbar, Wheelbarrow
     Answer: Wheelbarrow
     Explanation: Wheelbarrow is a class II lever; others are class I levers.


  9. Single fixed pulley, Class I lever, Class II lever, Class III lever
     Answer: Single fixed pulley
     Explanation: Pulley is not a lever; others are lever types.


  10. Friction, Weight of moving parts, Effort arm, Energy loss
     Answer: Effort arm
     Explanation: Effort arm is part of lever geometry; others reduce efficiency.


  11. Human forearm, Tweezers, Tongs, Crowbar
     Answer: Crowbar
     Explanation: Crowbar is a class I lever; others are class III levers.


  12. Standing on toes, Wheelbarrow, Nutcracker, Scissors
     Answer: Scissors
     Explanation: Scissors are class I; others are class II levers.


  13. Single fixed pulley, Single movable pulley, Block and tackle, Crowbar
     Answer: Crowbar
     Explanation: Crowbar is a lever; others are pulleys.


  14. VR = 1, VR = 2, VR = 4, VR = 0.5
     Answer: VR = 0.5
     Explanation: VR cannot be less than 1 for these ideal machines.


  15. Newton, Joule, Watt, MA
     Answer: MA
     Explanation: MA is dimensionless; others are SI units.


  16. Fulcrum, Supporting strand, Load, Effort
     Answer: Supporting strand
     Explanation: Supporting strand is a pulley term; others are common to all machines.


  17. Force multiplier, Speed multiplier, Crowbar, Efficiency
     Answer: Efficiency
     Explanation: Efficiency is a measure; others describe machine types.


  18. Crowbar, Nutcracker, Wheelbarrow, Standing on toes
     Answer: Crowbar
     Explanation: Crowbar is class I; others are class II levers.


  19. MA = L/E, VR = dE/dL, η = MA/VR, Work = Power × Time
     Answer: Work = Power × Time
     Explanation: This is a general physics formula; others are machine-specific formulas.


  20. Lever, Pulley, Inclined plane, Generator
     Answer: Generator
     Explanation: Generator is not a simple machine.


  21. Tweezers, Tongs, Forearm, Nutcracker
     Answer: Nutcracker
     Explanation: Nutcracker is class II; others are class III levers.


  22. Scissors, Pliers, Seesaw, Bottle opener
     Answer: Bottle opener
     Explanation: Bottle opener is class II; others are class I levers.


  23. Rope tension, VR, MA, η
     Answer: Rope tension
     Explanation: Rope tension is a force; others are ratios.


  24. Crowbar, Nodding head, Scissors, Wheelbarrow
     Answer: Wheelbarrow
     Explanation: Wheelbarrow is class II; others are class I levers.


  25. Newton, No unit, Joule, Watt
     Answer: No unit
     Explanation: “No unit” is not an SI unit.


  26. First class lever, Second class lever, Third class lever, Block and tackle
     Answer: Block and tackle
     Explanation: It is a pulley system, not a lever.


  27. Load, Effort, MA, Momentum
     Answer: Momentum
     Explanation: Momentum is unrelated to basic machine terms.


  28. Ideal machine, Real machine, Lever, Motor
     Answer: Motor
     Explanation: Motor is not a simple machine discussed here.


  29. MA = 1, VR = 1, η = 100%, MA = 5
     Answer: MA = 5
     Explanation: In a single fixed pulley, MA is 1, not 5.


  30. Friction, VR, MA, Efficiency
     Answer: Friction
     Explanation: Friction is a cause of loss; others are performance measures.


  31. Standing on toes, Wheelbarrow, Nutcracker, Human forearm
     Answer: Human forearm
     Explanation: Forearm is class III; others are class II.


  32. Effort arm, Load arm, Pulley block, Fulcrum
     Answer: Pulley block
     Explanation: Pulley block belongs to pulley system; others are lever parts.


  33. 100%, 80%, 60%, 120% efficiency
     Answer: 120% efficiency
     Explanation: Efficiency cannot exceed 100%.


  34. Crowbar, Scissors, Pliers, Tongs
     Answer: Tongs
     Explanation: Tongs are class III; others are class I.


  35. Single fixed pulley, Single movable pulley, Double fixed pulley, Block and tackle
     Answer: Double fixed pulley
     Explanation: Double fixed pulley is not a standard type covered here.


  36. Wheelbarrow, Nutcracker, Standing on toes, Fishing rod
     Answer: Fishing rod
     Explanation: Fishing rod is class III; others are class II levers.


  37. Class I, Class II, Class III, Class IV
     Answer: Class IV
     Explanation: There is no class IV lever.


  38. Effort, Load, Energy, MA
     Answer: Energy
     Explanation: Energy is a general concept; others are specific to machine operation.


  39. VR, MA, η, Work done per second
     Answer: Work done per second
     Explanation: This is power; others are machine ratios.


  40. Seesaw, Crowbar, Nutcracker, Scissors
     Answer: Nutcracker
     Explanation: Nutcracker is class II; others are class I levers.


  41. Upper block, Lower block, Effort arm, Supporting strand
     Answer: Effort arm
     Explanation: Effort arm is a lever term; others are pulley parts.


  42. Nodding head, Wheelbarrow, Nutcracker, Standing on toes
     Answer: Nodding head
     Explanation: Nodding head is class I; others are class II levers.


  43. Pulley rope, Fulcrum, Load, Effort
     Answer: Pulley rope
     Explanation: Pulley rope is specific to pulley; others apply to all machines.


  44. Block and tackle, Inclined plane, Lever, Crowbar
     Answer: Crowbar
     Explanation: Crowbar is a specific lever; others are general machine types.


  45. Tweezers, Forearm, Fishing rod, Bottle opener
     Answer: Bottle opener
     Explanation: Bottle opener is class II; others are class III levers.


  46. 2N, 4N, 6N, 6m/s
     Answer: 6m/s
     Explanation: 6m/s is a speed; others are forces.


  47. MA > 1, MA = 1, MA < 1, η > 1
     Answer: η > 1
     Explanation: Efficiency cannot be greater than 1.


  48. Lever, Pulley, Screw, Turbine
     Answer: Turbine
     Explanation: Turbine is not a simple machine discussed here.


  49. Rope, Pulley wheel, Effort arm, Pulley axle
     Answer: Effort arm
     Explanation: Effort arm is a lever part; others are pulley parts.


  50. First class lever, Second class lever, Third class lever, Gear train
     Answer: Gear train
     Explanation: Gear train is not covered in this chapter.

Match the Pair

Set 1 – Match the Pair
 Column A:

  1. Mechanical advantage
  2. Velocity ratio
  3. Efficiency
  4. Effort arm
  5. Load arm

Column B:
 a) Distance from load to fulcrum
 b) Ratio of work output to work input
 c) Distance from effort to fulcrum
 d) Ratio of load to effort
 e) Ratio of effort distance to load distance

Answers (Set 1):
 1 – d
 2 – e
 3 – b
 4 – c
 5 – a




Set 2 – Match the Pair
 Column A:

  1. Crowbar
  2. Nutcracker
  3. Tweezers
  4. Wheelbarrow
  5. Nodding head

Column B:
 a) Class I lever
 b) Class III lever
 c) Class II lever
 d) Class I lever (human body)
 e) Class II lever

Answers (Set 2):
 1 – a
 2 – c
 3 – b
 4 – e
 5 – d




Set 3 – Match the Pair
 Column A:

  1. Single fixed pulley
  2. Single movable pulley
  3. Block and tackle (4 strands)
  4. VR of single fixed pulley
  5. VR of single movable pulley

Column B:
 a) VR = 4
 b) Changes direction only
 c) VR = 2
 d) VR = 1
 e) Used to multiply force

Answers (Set 3):
 1 – b
 2 – e
 3 – a
 4 – d
 5 – c




Set 4 – Match the Pair
 Column A:

  1. Principle of lever
  2. Work input
  3. Work output
  4. Ideal machine
  5. Real machine

Column B:
 a) Output less than input
 b) Load × Load distance
 c) Input = Output
 d) Effort × Effort distance
 e) Load × load arm = Effort × effort arm

Answers (Set 4):
 1 – e
 2 – d
 3 – b
 4 – c
 5 – a




Set 5 – Match the Pair
 Column A:

  1. Speed multiplier
  2. Force multiplier
  3. MA > 1
  4. MA < 1
  5. MA = 1

Column B:
 a) Single fixed pulley
 b) Effort moves more than load
 c) Effort arm longer than load arm
 d) Effort arm shorter than load arm
 e) Load arm shorter than effort arm

Answers (Set 5):
 1 – b
 2 – e
 3 – c
 4 – d
 5 – a




Set 6 – Match the Pair
 Column A:

  1. Friction
  2. Weight of moving parts
  3. η in practical machine
  4. η in ideal machine
  5. Reason for MA < VR

Column B:
 a) Causes energy loss
 b) Reduces efficiency
 c) Efficiency less than 100%
 d) Efficiency equals 100%
 e) Friction and moving parts’ weight

Answers (Set 6):
 1 – a
 2 – b
 3 – c
 4 – d
 5 – e




Set 7 – Match the Pair
 Column A:

  1. Human forearm
  2. Standing on toes
  3. Scissors
  4. Bottle opener
  5. Pliers

Column B:
 a) Class II lever
 b) Class III lever
 c) Class I lever
 d) Class II lever
 e) Class I lever

Answers (Set 7):
 1 – b
 2 – a
 3 – c
 4 – d
 5 – e




Set 8 – Match the Pair
 Column A:

  1. MA formula
  2. VR formula
  3. Efficiency formula
  4. Work output formula
  5. Work input formula

Column B:
 a) (MA / VR) × 100%
 b) L / E
 c) dE / dL
 d) Load × Load distance
 e) Effort × Effort distance

Answers (Set 8):
 1 – b
 2 – c
 3 – a
 4 – d
 5 – e




Set 9 – Match the Pair
 Column A:

  1. Unit of load
  2. Unit of effort
  3. Unit of work
  4. Unit of power
  5. Unit of efficiency

Column B:
 a) Watt
 b) Newton
 c) Newton
 d) No unit
 e) Joule

Answers (Set 9):
 1 – b
 2 – c
 3 – e
 4 – a
 5 – d



Set 10 – Match the Pair
 Column A:

  1. VR of ideal block and tackle with 3 strands
  2. VR of single fixed pulley
  3. MA of ideal single movable pulley
  4. MA of ideal single fixed pulley
  5. VR of ideal single movable pulley

Column B:
 a) VR = 1
 b) MA = 1
 c) VR = 3
 d) MA = 2
 e) VR = 2

Answers (Set 10):
 1 – c
 2 – a
 3 – d
 4 – b
 5 – e

Short Answer Questions  

  1. What is a machine?
     Answer: A machine is a device that makes our work easier by multiplying force, changing its direction, or gaining speed.


  2. Define effort.
     Answer: Effort is the force applied to a machine.


  3. Define load.
     Answer: Load is the resistance that the machine overcomes.


  4. What is mechanical advantage?
     Answer: Mechanical advantage is the ratio of load to effort (MA = L/E).


  5. What is velocity ratio?
     Answer: Velocity ratio is the ratio of distance moved by effort to distance moved by load (VR = dE/dL).


  6. Define efficiency of a machine.
     Answer: Efficiency is the ratio of work output to work input, expressed as a percentage.


  7. Write the relation between efficiency, MA, and VR.
     Answer: η = (MA / VR) × 100%.


  8. State the principle of a lever.
     Answer: The principle of a lever is that load × load arm = effort × effort arm.


  9. What is the load arm of a lever?
     Answer: It is the distance from the load to the fulcrum.


  10. What is the effort arm of a lever?
     Answer: It is the distance from the effort to the fulcrum.


  11. Which class of lever has fulcrum between effort and load?
     Answer: Class I lever.


  12. Give one example of a class I lever.
     Answer: Crowbar.


  13. Which class of lever has load between fulcrum and effort?
     Answer: Class II lever.


  14. Give one example of a class II lever.
     Answer: Nutcracker.


  15. Which class of lever has effort between fulcrum and load?
     Answer: Class III lever.


  16. Give one example of a class III lever.
     Answer: Tweezers.


  17. What is the VR of a single fixed pulley?
     Answer: 1.


  18. What is the VR of a single movable pulley?
     Answer: 2.


  19. What is the ideal MA of a single movable pulley?
     Answer: 2.


  20. Name the pulley system in which VR equals the number of supporting strands.
     Answer: Block and tackle system.


  21. What is the main function of a single fixed pulley?
     Answer: To change the direction of effort.


  22. What is the main function of a single movable pulley?
     Answer: To multiply force.


  23. State one cause for the efficiency of a real machine being less than 100%.
     Answer: Friction.


  24. Name another cause for the efficiency of a real machine being less than 100%.
     Answer: Weight of moving parts.


  25. Define work input.
     Answer: Work input = effort × effort distance.


  26. Define work output.
     Answer: Work output = load × load distance.


  27. What is the MA of an ideal single fixed pulley?
     Answer: 1.


  28. What is a speed multiplier?
     Answer: A machine in which effort moves more than the load and MA < 1.


  29. What is a force multiplier?
     Answer: A machine in which load moves more than the effort and MA > 1.


  30. Give an example of a speed multiplier.
     Answer: Scissors.


  31. Give an example of a force multiplier.
     Answer: Wheelbarrow.


  32. State the unit of effort.
     Answer: Newton.


  33. State the unit of load.
     Answer: Newton.


  34. State the unit of work.
     Answer: Joule.


  35. State the unit of power.
     Answer: Watt.


  36. State the unit of MA.
     Answer: No unit.


  37. State the unit of VR.
     Answer: No unit.


  38. State the unit of efficiency.
     Answer: No unit.


  39. In which class of lever is the mechanical advantage always greater than 1?
     Answer: Class II lever.


  40. In which class of lever is the mechanical advantage always less than 1?
     Answer: Class III lever.


  41. In which class of lever can MA be greater than, equal to, or less than 1?
     Answer: Class I lever.


  42. What is the VR of a block and tackle with 3 strands?
     Answer: 3.


  43. Which part of the lever is fixed?
     Answer: Fulcrum.


  44. Name the lever type in human forearm lifting a weight.
     Answer: Class III lever.


  45. Name the lever type in standing on toes.
     Answer: Class II lever.


  46. Name the lever type in nodding the head.
     Answer: Class I lever.


  47. Which factor can increase MA in levers?
     Answer: Increasing effort arm length.


  48. Which factor can reduce MA in pulleys?
     Answer: Weight of moving pulleys.


  49. Name one advantage of using a pulley system.
     Answer: Reduces effort required to lift a load.


  50. Name one disadvantage of using a pulley system.
     Answer: Efficiency is reduced due to friction and weight of pulleys.

Puzzles

  1. I am a lever with fulcrum in the middle; my MA can be less, equal, or more than 1. What am I?
     Answer: Class I lever.


  2. I am a lever where load is between fulcrum and effort. What am I?
     Answer: Class II lever.


  3. I am a lever where effort is between fulcrum and load. What am I?
     Answer: Class III lever.


  4. I have VR = 1, MA = 1 ideally, and only change direction of effort. What am I?
     Answer: Single fixed pulley.


  5. I have VR = 2 and halve the effort needed to lift a load. What am I?
     Answer: Single movable pulley.


  6. I have many pulleys in two blocks and VR equals the number of strands. What am I?
     Answer: Block and tackle system.


  7. I am the pivot point of a lever. What am I?
     Answer: Fulcrum.


  8. I am the ratio of load to effort. What am I?
     Answer: Mechanical Advantage.


  9. I am the ratio of distance moved by effort to distance moved by load. What am I?
     Answer: Velocity Ratio.


  10. I am the ratio of work output to work input × 100%. What am I?
     Answer: Efficiency.


  11. I am a lever used to crack nuts. What am I?
     Answer: Nutcracker (Class II lever).


  12. I am a lever used in a human forearm. What am I?
     Answer: Class III lever.


  13. I am a lever used in scissors. What am I?
     Answer: Class I lever.


  14. I am a lever used in tweezers. What am I?
     Answer: Class III lever.


  15. I am a lever used in a wheelbarrow. What am I?
     Answer: Class II lever.


  16. I am the distance from load to fulcrum. What am I?
     Answer: Load arm.


  17. I am the distance from effort to fulcrum. What am I?
     Answer: Effort arm.


  18. I am the load in a pulley supported equally by two strands. What am I?
     Answer: Single movable pulley load.


  19. I am the main cause why efficiency is never 100%. What am I?
     Answer: Friction.


  20. I am a method to reduce friction in machines. What am I?
     Answer: Lubrication.


  21. I am the weight of moving parts in a machine; I reduce efficiency. What am I?
     Answer: Self-weight of machine parts.


  22. I am a machine that increases speed of motion; MA < 1. What am I?
     Answer: Speed multiplier.


  23. I am a machine that multiplies force; MA > 1. What am I?
     Answer: Force multiplier.


  24. I am measured in Newtons when referring to load. What am I?
     Answer: Load force.


  25. I am measured in Newtons when referring to effort. What am I?
     Answer: Effort force.


  26. I am the SI unit of work. What am I?
     Answer: Joule.


  27. I am the SI unit of power. What am I?
     Answer: Watt.


  28. I am the lever action in standing on toes. What am I?
     Answer: Class II lever.


  29. I am the lever action in nodding the head. What am I?
     Answer: Class I lever.


  30. I am the formula MA = L/E. What do I represent?
     Answer: Mechanical Advantage.


  31. I am the formula VR = dE/dL. What do I represent?
     Answer: Velocity Ratio.


  32. I am the formula η = (MA/VR) × 100%. What do I represent?
     Answer: Efficiency.


  33. I am a lever that can have MA more than, less than, or equal to 1. What am I?
     Answer: Class I lever.


  34. I am the main reason for MA < VR in real machines. What am I?
     Answer: Energy losses due to friction.


  35. I am an ideal condition where MA = VR. What am I?
     Answer: Ideal machine.


  36. I am a lever where both arms are equal; my MA is 1. What am I?
     Answer: Class I lever with equal arms.


  37. I am a rope in a pulley system; I must move a long distance to lift the load. What am I?
     Answer: Effort rope.


  38. I am the mechanical benefit of using a longer effort arm. What am I?
     Answer: Increased MA.


  39. I am a disadvantage of using a thick rope in pulleys. What am I?
     Answer: Increased friction.


  40. I am an example of a speed multiplier in cutting cloth. What am I?
     Answer: Scissors.


  41. I am an example of a force multiplier used in gardens. What am I?
     Answer: Spade.


  42. I am a machine with VR determined only by geometry. What am I?
     Answer: Ideal machine.


  43. I am an example of a class II lever in the kitchen. What am I?
     Answer: Lemon squeezer.


  44. I am an example of a class III lever in sports. What am I?
     Answer: Hockey stick.


  45. I am the factor that can be increased to get higher MA in a lever. What am I?
     Answer: Effort arm length.


  46. I am the point that must be fixed for a lever to work. What am I?
     Answer: Fulcrum.


  47. I am the part of a lever that moves less distance in a speed multiplier. What am I?
     Answer: Load.


  48. I am the part of a lever that moves more distance in a force multiplier. What am I?
     Answer: Effort.


  49. I am the VR of a block and tackle with 5 strands. What am I?
     Answer: 5.


  50. I am the main use of a single fixed pulley even though MA = 1. What am I?
     Answer: Changing the direction of effort.

Difference Between:

  1. Difference between Ideal Machine and Real Machine
     Answer:
  • Ideal Machine: 100% efficiency, no energy loss, MA = VR, friction absent.
  • Real Machine: Efficiency < 100%, energy loss due to friction, MA < VR, friction present.



  1. Difference between Mechanical Advantage (MA) and Velocity Ratio (VR)
    Answer:
  • MA: Ratio of load to effort; affected by friction; measures force multiplication.
  • VR: Ratio of distance moved by effort to distance moved by load; unaffected by friction; determined by machine design.



  1. Difference between Single Fixed Pulley and Single Movable Pulley
    Answer:
  • Single Fixed Pulley: VR = 1, MA = 1 (ideal), only changes direction of effort.
  • Single Movable Pulley: VR = 2, MA ≈ 2 (ideal), reduces effort needed to lift load.



  1. Difference between Force Multiplier and Speed Multiplier
    Answer:
  • Force Multiplier: MA > 1; effort is less than load; used for lifting heavy loads.
  • Speed Multiplier: MA < 1; effort moves more distance; used for high-speed motion of load.



  1. Difference between Class I Lever and Class II Lever
    Answer:
  • Class I Lever: Fulcrum between effort and load; MA can be <, =, or > 1.
  • Class II Lever: Load between fulcrum and effort; MA always > 1.



  1. Difference between Class I Lever and Class III Lever
    Answer:
  • Class I Lever: Fulcrum in the middle; MA can vary.
  • Class III Lever: Effort between fulcrum and load; MA always < 1.



  1. Difference between Class II Lever and Class III Lever
    Answer:
  • Class II Lever: Load in the middle; MA > 1; force multiplier.
  • Class III Lever: Effort in the middle; MA < 1; speed multiplier.



  1. Difference between Effort Arm and Load Arm
    Answer:
  • Effort Arm: Distance from fulcrum to point where effort is applied.
  • Load Arm: Distance from fulcrum to point where load is applied.



  1. Difference between Work Input and Work Output
    Answer:
  • Work Input: Effort × distance moved by effort; total energy supplied.
  • Work Output: Load × distance moved by load; useful energy obtained.



  1. Difference between Efficiency and Mechanical Advantage
    Answer:
  • Efficiency: Percentage ratio of work output to work input; indicates performance.
  • MA: Ratio of load to effort; indicates force multiplication.



  1. Difference between Friction and Lubrication
    Answer:
  • Friction: Force opposing motion; reduces efficiency; causes wear.
  • Lubrication: Process of reducing friction; increases efficiency; prolongs machine life.



  1. Difference between Single Pulley and Block and Tackle System
    Answer:
  • Single Pulley: One wheel; VR ≤ 2; limited force multiplication.
  • Block and Tackle: Multiple pulleys in blocks; VR equals number of strands; high force multiplication.



  1. Difference between Movable Pulley and Fixed Pulley
    Answer:
  • Movable Pulley: Moves with load; reduces effort; VR > 1.
  • Fixed Pulley: Stays in position; changes direction of effort; VR = 1.



  1. Difference between Speed Multiplier Machine and Force Multiplier Machine
    Answer:
  • Speed Multiplier: MA < 1; load moves faster; example – scissors.
  • Force Multiplier: MA > 1; load moves slower but requires less effort; example – crowbar.



  1. Difference between Ideal Lever and Real Lever
    Answer:
  • Ideal Lever: No friction; MA = VR; efficiency = 100%.
  • Real Lever: Friction present; MA < VR; efficiency < 100%.



  1. Difference between Law of the Lever and Principle of Moments
    Answer:
  • Law of the Lever: Effort × effort arm = Load × load arm (ideal).
  • Principle of Moments: For equilibrium, sum of clockwise moments = sum of anticlockwise moments.



  1. Difference between Load and Effort
    Answer:
  • Load: Resistance overcome by machine; measured in Newtons.
  • Effort: Force applied to operate the machine; measured in Newtons.



  1. Difference between Work Done and Power
    Answer:
  • Work Done: Force × distance; measured in Joules.
  • Power: Work done per unit time; measured in Watts.



  1. Difference between Moment and Torque
    Answer:
  • Moment: Turning effect of force about a point; generally in levers.
  • Torque: Rotational effect of force in machines like wheels; often used for circular motion.



  1. Difference between Theoretical MA and Actual MA
    Answer:
  • Theoretical MA: Calculated assuming no friction; equals VR in ideal case.
  • Actual MA: Measured in real conditions; always less than theoretical MA due to energy losses.

Assertion and Reason

  1. Assertion: A machine can have an efficiency of more than 100%.
     Reason: In an ideal machine, there is no energy loss.
     Answer: Both Assertion and Reason are false.


  2. Assertion: Mechanical advantage has no unit.
     Reason: It is a ratio of two similar quantities (forces).
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  3. Assertion: For a practical machine, MA < VR.
     Reason: Friction and weight of moving parts reduce efficiency.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  4. Assertion: Efficiency of an ideal machine is 100%.
     Reason: There is no energy loss in an ideal machine.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  5. Assertion: A single fixed pulley changes the direction of effort.
     Reason: Its VR = 1.
     Answer: Both Assertion and Reason are true, but Reason is not the correct explanation.


  6. Assertion: A crowbar is a class II lever.
     Reason: In it, the load is between fulcrum and effort.
     Answer: Both Assertion and Reason are false.


  7. Assertion: In a speed multiplier, MA < 1.
     Reason: The effort moves a greater distance than the load.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  8. Assertion: VR of a block and tackle equals the number of supporting strands.
     Reason: Each supporting strand shares the load equally.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  9. Assertion: A nutcracker is a class I lever.
     Reason: The fulcrum lies between effort and load.
     Answer: Both Assertion and Reason are false.


  10. Assertion: Friction increases the efficiency of a machine.
     Reason: It reduces the work output.
     Answer: Assertion is false, Reason is true.


  11. Assertion: MA = VR for an ideal machine.
     Reason: Efficiency is 100% for an ideal machine.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  12. Assertion: The effort arm is the distance from effort to load.
     Reason: The effort arm is measured from effort to fulcrum.
     Answer: Assertion is false, Reason is true.


  13. Assertion: In a single movable pulley, VR = 2 ideally.
     Reason: The load is supported by two strands of rope.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  14. Assertion: Tweezers are class III levers.
     Reason: The effort is between the fulcrum and the load.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  15. Assertion: MA of a class II lever is less than 1.
     Reason: Effort arm is longer than load arm.
     Answer: Assertion is false, Reason is false.


  16. Assertion: Efficiency is always less than 100% for real machines.
     Reason: Some energy is lost as heat due to friction.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  17. Assertion: Wheelbarrow is a class I lever.
     Reason: The fulcrum is between effort and load.
     Answer: Both Assertion and Reason are false.


  18. Assertion: A lever works on the principle of conservation of energy.
     Reason: Neglecting friction, work input equals work output.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  19. Assertion: VR has no unit.
     Reason: It is a ratio of two distances.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  20. Assertion: In class III levers, MA > 1.
     Reason: Effort arm is shorter than load arm.
     Answer: Assertion is false, Reason is true.


  21. Assertion: In a block and tackle, VR increases with more pulleys.
     Reason: More pulleys increase the number of supporting strands.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  22. Assertion: A single fixed pulley is used as a force multiplier.
     Reason: MA of a single fixed pulley is more than 1.
     Answer: Both Assertion and Reason are false.


  23. Assertion: Standing on toes is a class II lever.
     Reason: Load is between the fulcrum and effort.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  24. Assertion: MA is the ratio of effort to load.
     Reason: MA = Load / Effort.
     Answer: Assertion is false, Reason is true.


  25. Assertion: The unit of efficiency is percent.
     Reason: Efficiency is calculated as a percentage.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  26. Assertion: All pulleys are used to change the direction of effort.
     Reason: In a single movable pulley, direction of effort remains same.
     Answer: Both Assertion and Reason are true, but Reason is not the correct explanation.


  27. Assertion: MA depends on friction in the machine.
     Reason: Friction reduces the output force for a given effort.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  28. Assertion: η = (VR / MA) × 100%.
     Reason: Efficiency is the ratio MA/VR × 100%.
     Answer: Assertion is false, Reason is true.


  29. Assertion: The load arm is measured from load to fulcrum.
     Reason: This is the definition of load arm in a lever.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  30. Assertion: Efficiency increases if friction increases.
     Reason: Friction converts useful energy into heat.
     Answer: Both Assertion and Reason are false.


  31. Assertion: MA of an ideal single movable pulley is 2.
     Reason: The load is supported by two strands of rope.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  32. Assertion: Nodding head is an example of a class III lever.
     Reason: Fulcrum lies between effort and load.
     Answer: Assertion is false, Reason is true.


  33. Assertion: In an ideal lever, increasing effort arm increases MA.
     Reason: MA is the ratio of effort arm to load arm.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  34. Assertion: VR = MA for all real machines.
     Reason: Friction is negligible in real machines.
     Answer: Both Assertion and Reason are false.


  35. Assertion: A lever can be used to multiply speed.
     Reason: In class III levers, effort moves more than the load.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  36. Assertion: Crowbar is a speed multiplier.
     Reason: MA of a crowbar is less than 1.
     Answer: Both Assertion and Reason are false.


  37. Assertion: η < 100% for real machines.
     Reason: Energy is lost due to friction and other resistances.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  38. Assertion: VR has a unit of metres.
     Reason: VR is a ratio of distances.
     Answer: Assertion is false, Reason is true.


  39. Assertion: The efficiency of a single fixed pulley is always less than 100%.
     Reason: Some work is done against friction.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  40. Assertion: MA = VR for an ideal single movable pulley.
     Reason: Efficiency is 100% in ideal case.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  41. Assertion: Load in a lever is measured in Joules.
     Reason: Joule is the SI unit of energy.
     Answer: Both Assertion and Reason are false.


  42. Assertion: In a block and tackle, MA can be reduced by heavy pulleys.
     Reason: The weight of moving pulleys adds to the load.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  43. Assertion: A speed multiplier has VR < 1.
     Reason: Effort moves a shorter distance than load.
     Answer: Both Assertion and Reason are false.


  44. Assertion: Scissors are class I levers.
     Reason: Fulcrum lies between effort and load.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  45. Assertion: MA is independent of the arrangement of pulleys.
     Reason: MA only depends on VR.
     Answer: Both Assertion and Reason are false.


  46. Assertion: η = (Work output / Work input) × 100%.
     Reason: Efficiency is ratio of useful work to total work done.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  47. Assertion: Effort arm is longer than load arm in a force multiplier.
     Reason: This gives MA > 1.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  48. Assertion: A single movable pulley cannot change the direction of effort.
     Reason: In it, the effort is applied in the same direction as load movement.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.


  49. Assertion: VR of a single fixed pulley is greater than 1.
     Reason: It multiplies force.
     Answer: Both Assertion and Reason are false.


  50. Assertion: Efficiency of a machine is always equal to MA/VR × 100%.
     Reason: This relation is derived from definition of efficiency.
     Answer: Both Assertion and Reason are true, and Reason is the correct explanation.

True or False

  1. A machine can multiply force.
     Answer: True


  2. A machine can produce more energy than it consumes.
     Answer: False


  3. Mechanical advantage is the ratio of load to effort.
     Answer: True


  4. Velocity ratio is the ratio of distance moved by effort to distance moved by load.
     Answer: True


  5. Efficiency is always greater than 100% for an ideal machine.
     Answer: False


  6. For a practical machine, MA is always greater than VR.
     Answer: False


  7. The SI unit of MA is Newton.
     Answer: False


  8. The SI unit of VR is no unit.
     Answer: True


  9. Efficiency has no unit.
     Answer: True


  10. A single fixed pulley changes the direction of effort.
     Answer: True


  11. The VR of a single fixed pulley is 2.
     Answer: False


  12. A single movable pulley has an ideal MA of 2.
     Answer: True


  13. In a block and tackle, VR equals the number of supporting strands.
     Answer: True


  14. The load arm is measured from load to fulcrum.
     Answer: True


  15. The effort arm is measured from effort to load.
     Answer: False


  16. A crowbar is a class I lever.
     Answer: True


  17. A nutcracker is a class III lever.
     Answer: False


  18. A wheelbarrow is a class II lever.
     Answer: True


  19. Tweezers are a class III lever.
     Answer: True


  20. Standing on toes is a class II lever.
     Answer: True


  21. Nodding the head is a class II lever.
     Answer: False


  22. Efficiency is reduced in real machines due to friction.
     Answer: True


  23. Efficiency is reduced in real machines due to the weight of moving parts.
     Answer: True


  24. Work input is equal to effort × effort distance.
     Answer: True


  25. Work output is equal to load × load distance.
     Answer: True


  26. For an ideal machine, MA = VR.
     Answer: True


  27. In a speed multiplier, MA > 1.
     Answer: False


  28. In a force multiplier, MA < 1.
     Answer: False


  29. Scissors are a class I lever.
     Answer: True


  30. Pliers are a class II lever.
     Answer: False


  31. In a class III lever, the effort is between fulcrum and load.
     Answer: True


  32. VR of a single fixed pulley is 1.
     Answer: True


  33. VR of a single movable pulley is 3.
     Answer: False


  34. VR has no unit.
     Answer: True


  35. MA has a unit of Newton.
     Answer: False


  36. Efficiency is expressed as a percentage.
     Answer: True


  37. Friction in a machine can be eliminated completely.
     Answer: False


  38. The principle of a lever is based on the principle of moments.
     Answer: True


  39. A class II lever always has MA greater than 1.
     Answer: True


  40. In an ideal machine, efficiency is 100%.
     Answer: True


  41. Block and tackle is a type of lever.
     Answer: False


  42. Crowbar is an example of a speed multiplier.
     Answer: False


  43. The load in a machine is measured in Newtons.
     Answer: True


  44. MA of a single fixed pulley is ideally 1.
     Answer: True


  45. MA of a single movable pulley is ideally 1.
     Answer: False


  46. In class I levers, fulcrum lies between load and effort.
     Answer: True


  47. MA of a speed multiplier is less than 1.
     Answer: True


  48. VR of a block and tackle with 5 strands is 5.
     Answer: True


  49. Efficiency can never be more than 100% in real machines.
     Answer: True


  50. Levers and pulleys are examples of simple machines.
     Answer: True

Long Answer Questions

  1. Define a machine. State its four main functions with examples.
     Answer: A machine is a device that makes our work easier by multiplying force, changing the direction of force, changing the point of application of force, or providing a gain in speed.
     Functions:
  • Acts as a force multiplier – e.g., crowbar.
  • Changes the point of application of effort – e.g., spanner.
  • Changes the direction of effort – e.g., single fixed pulley.
  • Provides a gain in speed – e.g., sewing machine wheel.



  1. Explain the terms load, effort, mechanical advantage, velocity ratio, and efficiency with their formulas.
    Answer:
  • Load (L): Resistance overcome by the machine.
  • Effort (E): Force applied to the machine.
  • Mechanical Advantage (MA): Ratio of load to effort, MA = L/E.
  • Velocity Ratio (VR): Ratio of distance moved by effort to distance moved by load, VR = dE/dL.
  • Efficiency (η): Ratio of work output to work input, η = (MA / VR) × 100%.



  1. State and explain the principle of a lever.
    Answer: The principle of a lever states that for a lever in equilibrium,
     Load × Load arm = Effort × Effort arm.
     This is based on the principle of moments, which says that the sum of clockwise moments equals the sum of anticlockwise moments about the fulcrum.


  2. Describe the three classes of levers with diagrams and examples.
    Answer:


  • Class I: Fulcrum between effort and load. Examples: crowbar, scissors. MA can be > 1, = 1, or < 1.
  • Class II: Load between fulcrum and effort. Examples: wheelbarrow, nutcracker. MA > 1.
  • Class III: Effort between fulcrum and load. Examples: tweezers, human forearm. MA < 1.



  1. What is a force multiplier? Give an example and explain why it is so.
    Answer: A force multiplier is a machine where the effort arm is longer than the load arm, giving MA > 1, allowing a small effort to lift a large load. Example: wheelbarrow.


  2. What is a speed multiplier? Give an example and explain why it is so.
    Answer: A speed multiplier is a machine where the effort arm is shorter than the load arm, giving MA < 1, and effort moves more than the load. Example: scissors for cutting cloth.


  3. Describe a single fixed pulley with diagram, functions, MA, VR, and efficiency.
    Answer:
     A single fixed pulley is a wheel fixed to a support with a rope running over it. It changes the direction of effort, MA = 1, VR = 1, and ideal efficiency is 100%. In practice, efficiency is slightly less due to friction in the axle.


  4. Describe a single movable pulley with diagram, functions, MA, VR, and efficiency.
    Answer:
     A single movable pulley is attached to the load and moves with it. MA (ideal) = 2, VR = 2. It reduces the effort required to lift a load. Efficiency is less than 100% due to friction and weight of the pulley.


  5. Explain a block and tackle system with 4 supporting strands.
    Answer:
     It consists of an upper block fixed to a support and a lower block attached to the load, each containing pulleys. The VR = number of supporting strands = 4. MA (ideal) = 4. Efficiency depends on friction and weight of pulleys.


  6. Why is MA less than VR in practical machines?
    Answer: In practical machines, friction between moving parts and the weight of the moving parts reduce the output force, making MA less than VR.


  7. Explain the effect of friction on the efficiency of a machine.
    Answer: Friction converts part of the input energy into heat, reducing the useful work output, which decreases the efficiency.


  8. Explain the effect of the weight of moving parts on the efficiency of a machine.
    Answer: The weight of moving parts adds to the load the effort must overcome, reducing mechanical advantage and efficiency.


  9. Explain the term ‘work input’ and ‘work output’ with formulas.
    Answer:
     Work input = Effort × Effort distance.
     Work output = Load × Load distance.
     For an ideal machine, work input = work output.


  10. What is an ideal machine?
    Answer: An ideal machine is one with 100% efficiency, where there is no loss of energy and work input equals work output.


  11. What is a real machine? How does it differ from an ideal machine?
    Answer: A real machine has efficiency less than 100% due to energy losses from friction and weight of moving parts. Unlike an ideal machine, work input is greater than work output.


  12. State three differences between MA and VR.
    Answer:
  • MA is the ratio of load to effort; VR is the ratio of effort distance to load distance.
  • MA is affected by friction; VR is not.
  • MA can be measured directly; VR is determined from the geometry of the machine.
  1. Explain with diagram how a lever in human body functions (example: human forearm).
    Answer: In the human forearm, the elbow acts as fulcrum, the biceps provide the effort between fulcrum and load (in the hand). It is a class III lever with MA < 1, designed for speed.


  2. Explain with diagram the lever action in standing on toes.
    Answer: In standing on toes, the ball of the foot is the fulcrum, the body weight acts as load between fulcrum and effort, and the calf muscles provide the effort. This is a class II lever with MA > 1.


  3. Explain with diagram the lever action in nodding the head.
    Answer: The fulcrum is between effort (neck muscles) and load (weight of head), making it a class I lever.


  4. Why is the efficiency of a single fixed pulley less than 100%?
    Answer: Due to friction in the pulley axle and possible stretch in the rope, some input work is wasted.


  5. How can the efficiency of a pulley system be increased?
    Answer: By using well-lubricated pulleys, reducing the weight of moving parts, and using low-friction ropes.


  6. Why is VR of a machine independent of friction?
    Answer: VR depends on the geometry and displacement of effort and load, which are unaffected by friction.


  7. How is MA affected by friction?
    Answer: Friction reduces the effective output force, thus reducing MA.


  8. Explain why the MA of a class II lever is always greater than 1.
    Answer: In class II levers, the effort arm is always longer than the load arm, increasing MA above 1.


  9. Explain why the MA of a class III lever is always less than 1.
    Answer: In class III levers, the effort arm is always shorter than the load arm, making MA less than 1.


  10. Why is a single movable pulley considered a force multiplier?
    Answer: It requires only half the effort to lift a load, effectively doubling the force applied.


  11. State three advantages of using a block and tackle system.
    Answer:


  • Reduces effort required to lift heavy loads.
  • Can lift very heavy loads using small effort.
  • Allows convenient positioning of effort application.



  1. State two disadvantages of a pulley system.
    Answer:
  • Efficiency is reduced due to friction.
  • More rope must be pulled, increasing effort distance.



  1. State two conditions for the equilibrium of a lever.
    Answer:
  • Sum of clockwise moments = sum of anticlockwise moments.
  • Lever must be rigid.



  1. Give one example each of a lever in daily life for Class I, Class II, and Class III.
    Answer: Class I – Scissors, Class II – Wheelbarrow, Class III – Tweezers.


  2. Explain why a class III lever is used in the human body despite having MA < 1.
    Answer: It provides greater speed and range of movement, which is more useful for tasks requiring agility.


  3. Explain the relation η = (MA / VR) × 100% with derivation.
    Answer: η = Work output / Work input × 100%. Work output = L × dL, Work input = E × dE. So η = (L/E) ÷ (dE/dL) × 100% = (MA / VR) × 100%.


  4. Why can efficiency never be greater than 100%?
    Answer: Because energy cannot be created; some is always lost due to resistance and friction.


  5. How does increasing the effort arm affect MA?
    Answer: Increasing effort arm increases MA by giving greater moment to the effort force.


  6. How does increasing the load arm affect MA?
    Answer: It decreases MA as the load has greater moment, requiring more effort.


  7. Why is VR always greater than or equal to MA in practical machines?
    Answer: Because friction and other losses reduce the output force, lowering MA.


  8. Explain the role of the fulcrum in a lever.
    Answer: The fulcrum is the pivot point around which the lever rotates, balancing the moments of effort and load.


  9. Why is the VR of a single movable pulley 2?
    Answer: Because the load is supported by two rope strands, each carrying half the load.


  10. Explain why using more pulleys in a block and tackle increases VR.
    Answer: Each additional pulley increases the number of supporting strands, reducing effort per strand.


  11. Why is efficiency of a pulley system less when using heavier pulleys?
    Answer: The effort must overcome both the load and the weight of the pulleys.


  12. Give one reason why we use a single fixed pulley even though MA = 1.
    Answer: It allows effort to be applied in a more convenient direction.


  13. Why is the rope in a pulley system sometimes pulled a greater distance than the load is raised?
    Answer: This is necessary to distribute the load over multiple strands, reducing required effort.


  14. Explain why a lever can be used both as a speed multiplier and force multiplier.
    Answer: By adjusting the positions of effort, load, and fulcrum, MA can be made > 1 or < 1.


  15. Why do we lubricate moving parts of machines?
    Answer: To reduce friction, thereby increasing efficiency and reducing wear.


  16. Why do we prefer light but strong materials for moving parts in machines?
    Answer: To reduce weight and improve efficiency while maintaining strength.


  17. Explain why VR of a machine cannot be less than 1.
    Answer: VR < 1 would mean load moves more than effort, which contradicts the design of simple machines.


  18. Why is MA of a single fixed pulley always 1 ideally?
    Answer: The load is supported by only one rope strand carrying the full load.


  19. Why is MA of a single movable pulley ideally 2?
    Answer: The load is supported by two rope strands, each carrying half the load.


  20. Why is MA reduced in a pulley system with friction?
    Answer: Part of the effort is wasted in overcoming friction instead of lifting the load.


  21. State one way to experimentally determine VR of a lever.
    Answer: Measure the displacement of the effort and the displacement of the load and divide effort displacement by load displacement.

Give Reasons

  1. Give reason: A machine cannot have efficiency greater than 100%.
     Answer: Some energy is always lost due to friction and weight of moving parts, so output can never exceed input.


  2. Give reason: MA of a practical machine is always less than VR.
     Answer: Friction and the weight of moving parts reduce the effective load lifted for a given effort.


  3. Give reason: Efficiency of a real machine is less than 100%.
     Answer: Part of the input energy is wasted in overcoming friction and moving the parts of the machine.


  4. Give reason: The VR of a machine is not affected by friction.
     Answer: VR depends only on the geometry and displacement of effort and load, not on energy losses.


  5. Give reason: MA of a single fixed pulley is 1.
     Answer: The pulley only changes the direction of effort and does not multiply the force.


  6. Give reason: A single fixed pulley is preferred for lifting loads vertically.
     Answer: It allows effort to be applied in a convenient downward direction using body weight.


  7. Give reason: A single movable pulley is called a force multiplier.
     Answer: It allows the effort to be less than the load by supporting the load with two rope strands.


  8. Give reason: The VR of a single movable pulley is 2.
     Answer: The load is supported by two strands, so the effort moves twice the distance of the load.


  9. Give reason: Efficiency of a pulley system decreases with heavier pulleys.
     Answer: The effort must overcome both the load and the weight of the pulleys.


  10. Give reason: MA of a class II lever is always greater than 1.
     Answer: The effort arm is always longer than the load arm.


  11. Give reason: MA of a class III lever is always less than 1.
     Answer: The effort arm is always shorter than the load arm.


  12. Give reason: MA of a class I lever can be greater than, equal to, or less than 1.
     Answer: The relative positions of effort, load, and fulcrum can be adjusted.


  13. Give reason: Scissors are class I levers.
     Answer: The fulcrum lies between the effort applied at the handles and the load at the blades.


  14. Give reason: Wheelbarrow is a class II lever.
     Answer: The load is between the fulcrum at the wheel and the effort at the handles.


  15. Give reason: Tweezers are class III levers.
     Answer: The effort is applied between the fulcrum and the load.


  16. Give reason: In a speed multiplier, MA < 1.
     Answer: The effort arm is shorter than the load arm, so effort moves more than load.


  17. Give reason: In a force multiplier, MA > 1.
     Answer: The effort arm is longer than the load arm, allowing a small effort to lift a large load.


  18. Give reason: Efficiency is expressed as a percentage.
     Answer: It is the ratio of work output to work input multiplied by 100.


  19. Give reason: MA is a pure number without units.
     Answer: It is the ratio of two forces having the same unit.


  20. Give reason: VR is a pure number without units.
     Answer: It is the ratio of two distances having the same unit.


  21. Give reason: Work input is always greater than work output in real machines.
     Answer: Some energy is lost as heat and sound due to friction.


  22. Give reason: Ideal machines do not exist in reality.
     Answer: All machines have some friction and weight in moving parts.


  23. Give reason: Lubrication increases efficiency.
     Answer: It reduces friction between moving parts.


  24. Give reason: MA is reduced by friction.
     Answer: Part of the effort is used to overcome friction instead of lifting the load.


  25. Give reason: VR of a block and tackle equals the number of supporting strands.
     Answer: Each strand supports part of the load, sharing the total load equally.


  26. Give reason: Efficiency of a block and tackle system is less than 100%.
     Answer: Some effort is wasted in overcoming friction in pulleys and ropes.


  27. Give reason: In a class III lever, the effort moves a greater distance than the load.
     Answer: The effort arm is shorter than the load arm.


  28. Give reason: Standing on toes is a class II lever.
     Answer: The load (body weight) is between the fulcrum (toe joint) and effort (calf muscles).


  29. Give reason: Nodding the head is a class I lever.
     Answer: The fulcrum (neck joint) lies between the load (head weight) and effort (neck muscles).


  30. Give reason: MA = VR for an ideal machine.
     Answer: There are no energy losses, so all input is converted to output.


  31. Give reason: MA < VR for a real machine.
     Answer: Some input energy is lost, reducing the output force.


  32. Give reason: Pulley systems require longer lengths of rope for greater VR.
     Answer: Increasing VR means effort moves more distance to lift the load.


  33. Give reason: Heavy moving parts reduce MA.
     Answer: The effort must overcome both the load and the extra weight.


  34. Give reason: The VR of a single fixed pulley is 1.
     Answer: The effort and load move equal distances.


  35. Give reason: The VR of a single movable pulley is greater than its MA in practice.
     Answer: Friction reduces MA but not VR.


  36. Give reason: Machines do not save work.
     Answer: They only change the way work is done; total work input is always equal or more than work output.


  37. Give reason: MA can be less than 1 in some machines.
     Answer: These machines are designed to increase speed rather than force.


  38. Give reason: In a sewing machine wheel, effort arm is longer than load arm.
     Answer: This allows the wheel to move faster, acting as a speed multiplier.


  39. Give reason: Crowbar can act as both force and speed multiplier.
     Answer: By changing positions of load and effort, MA can be > 1 or < 1.


  40. Give reason: Efficiency increases when friction is reduced.
     Answer: Less input energy is wasted, so more is converted into useful work.


  41. Give reason: A pulley system allows lifting heavy loads with small effort.
     Answer: The load is shared among multiple supporting strands.


  42. Give reason: Efficiency decreases if rope is thick and rough.
     Answer: Thick rough ropes cause more friction over the pulley wheel.


  43. Give reason: Using ball bearings in machines increases efficiency.
     Answer: Ball bearings reduce rolling friction compared to sliding friction.


  44. Give reason: In real machines, MA depends on load.
     Answer: Frictional forces may vary with load, affecting MA.


  45. Give reason: In a class I lever, effort arm equal to load arm gives MA = 1.
     Answer: Both arms produce equal moments for equal forces.


  46. Give reason: MA of a class III lever is less than 1.
     Answer: The load arm is longer than the effort arm.


  47. Give reason: VR of a machine can never be less than 1.
     Answer: This would require the load to move more than the effort, which is not possible in simple machines.


  48. Give reason: Efficiency of an ideal machine is 100%.
     Answer: There is no loss of energy, so all input work becomes output work.


  49. Give reason: VR is determined by the design of the machine.
     Answer: It depends only on distances moved by effort and load.


  50. Give reason: MA is affected by wear and tear of machine parts.
     Answer: Worn parts increase friction, reducing output force for a given effort.

Arrange the Words 

Case Studies

Case Study 1:
 A gardener uses a spade to dig soil. The effort is applied far from the fulcrum and the load is near the fulcrum.
 Question: Which type of lever is this and is it a force or speed multiplier?
 Answer: Class I lever; acts as a force multiplier.

 

Case Study 2:
 A mechanic uses a wheelbarrow to move bricks from one place to another.
 Question: Which class of lever is this and why is MA > 1?
 Answer: Class II lever; effort arm is longer than load arm.

 

Case Study 3:
 A tailor cuts cloth using scissors. The scissors have long handles and short blades.
 Question: What type of lever is this and what is its function?
 Answer: Class I lever; acts as a speed multiplier.

 

Case Study 4:
 A man uses a crowbar to lift a heavy stone by placing a small block as the pivot point.
 Question: Which class of lever is used here?
 Answer: Class I lever.

 

Case Study 5:
 A person draws water from a well using a single fixed pulley.
 Question: What is the VR and MA of this pulley?
 Answer: VR = 1; MA = 1 (ideal), only changes direction of effort.

 

Case Study 6:
 A construction worker uses a single movable pulley to lift a bag of cement.
 Question: What is the VR of the system and why is it a force multiplier?
 Answer: VR = 2; load is supported by two strands, reducing effort.

 

Case Study 7:
 A sailor uses a block and tackle system with 4 strands to hoist a sail.
 Question: What is the VR and what happens to effort?
 Answer: VR = 4; effort is reduced to one-fourth of load (ideal).

 

Case Study 8:
 A child uses tweezers to pick up small beads.
 Question: Which class of lever is this and why is MA < 1?
 Answer: Class III lever; effort arm is shorter than load arm.

 

Case Study 9:
 A farmer lifts a bucket of water using a pulley arrangement with 3 supporting strands.
 Question: What is the VR and why is efficiency less than 100%?
 Answer: VR = 3; efficiency reduced due to friction and rope weight.

 

Case Study 10:
 A mason uses a nutcracker to break nutshells.
 Question: Which class of lever is this and why is it effective?
 Answer: Class II lever; long effort arm increases MA (> 1).

 

Case Study 11:
 A shopkeeper uses a pair of tongs to serve sugar cubes.
 Question: Which class of lever is this and is it a speed or force multiplier?
 Answer: Class III lever; acts as a speed multiplier.

 

Case Study 12:
 A worker uses a long-handled spade to lift sand quickly.
 Question: If MA < 1, what advantage does the worker get?
 Answer: Greater speed of load movement.

 

Case Study 13:
 A cyclist uses the pedals to turn the wheel through a chain mechanism.
 Question: Is this a speed or force multiplier?
 Answer: Speed multiplier; effort moves more distance than load.

 

Case Study 14:
 In a physics lab, a student uses a lever where fulcrum is at one end, load in the middle, and effort at the other end.
 Question: Which class of lever is this?
 Answer: Class II lever.

 

Case Study 15:
 A pulley system is designed with 5 strands supporting the load.
 Question: What is the VR and what is the effort for a 500 N load (ideal)?
 Answer: VR = 5; effort = 100 N.

 

Case Study 16:
 A person oils the moving parts of a sewing machine.
 Question: Why does this increase efficiency?
 Answer: Lubrication reduces friction, so more input energy becomes output.

 

Case Study 17:
 A person uses a screwdriver to open a paint can lid by prying it upwards.
 Question: Which class of lever is this?
 Answer: Class I lever.

 

Case Study 18:
 A blacksmith uses long tongs to lift hot metal pieces quickly from the furnace.
 Question: What type of lever is this and why is MA < 1?
 Answer: Class III lever; effort arm is shorter than load arm.

 

Case Study 19:
 A block and tackle with VR = 6 is used to lift a heavy crate, but the actual MA is 5.
 Question: Why is MA less than VR?
 Answer: Due to energy losses from friction and weight of pulleys.

 

Case Study 20:
 A fisherman uses a pulley to lift a net full of fish into the boat.
 Question: If VR = 2 and load = 200 N, what is the ideal effort required?
 Answer: Effort = 100 N.

Numericals

Q1. A machine lifts a load of 400 N when an effort of 100 N is applied. Find the MA.
 Answer: MA = Load / Effort = 400 / 100 = 4.
 Explanation: MA is the ratio of load to effort.

 

Q2. A machine has an MA of 5 and an effort of 60 N. Find the load it can lift.
 Answer: Load = MA × Effort = 5 × 60 = 300 N.
 Explanation: Rearrange MA = Load / Effort to find Load.

 

Q3. A machine’s VR is 4, and MA is 3.2. Find the efficiency.
 Answer: η = (MA / VR) × 100% = (3.2 / 4) × 100 = 80%.
 Explanation: Efficiency is the ratio MA/VR × 100%.

 

Q4. A machine lifts a load through 2 m when the effort moves 8 m. Find VR.
 Answer: VR = dE / dL = 8 / 2 = 4.
 Explanation: VR is distance moved by effort over distance moved by load.

 

Q5. A machine’s VR is 6 and its efficiency is 75%. Find the MA.
 Answer: MA = η × VR / 100 = 75 × 6 / 100 = 4.5.
 Explanation: Efficiency formula rearranged to get MA.

 

Q6. An effort of 120 N lifts a load of 300 N with VR = 4. Find the efficiency.
 Answer: MA = 300 / 120 = 2.5; η = (2.5 / 4) × 100 = 62.5%.

 

Q7. A lever lifts a load of 200 N using 50 N effort. Find MA.
 Answer: MA = 200 / 50 = 4.

 

Q8. A lever has effort arm 2 m and load arm 0.5 m. Find VR.
 Answer: VR = Effort Arm / Load Arm = 2 / 0.5 = 4.

 

Q9. A lever lifts a 600 N load with 200 N effort and VR = 4. Find efficiency.
 Answer: MA = 600 / 200 = 3; η = (3 / 4) × 100 = 75%.

 

Q10. A block and tackle has 5 strands and lifts 500 N load. Find VR and ideal effort.
 Answer: VR = 5; Effort = 500 / 5 = 100 N.

 

Q11. A machine has η = 80%, VR = 5. Find MA.
 Answer: MA = 0.8 × 5 = 4.

 

Q12. A machine has MA = 4, Effort = 60 N. Find Load.
 Answer: Load = 4 × 60 = 240 N.

 

Q13. VR = 3, MA = 2.4. Find efficiency.
 Answer: η = (2.4 / 3) × 100 = 80%.

 

Q14. A lever has effort arm 1.5 m, load arm 0.5 m. Find VR.
 Answer: VR = 1.5 / 0.5 = 3.

 

Q15. VR = 2, Efficiency = 85%. Find MA.
 Answer: MA = 0.85 × 2 = 1.7.

 

Q16. Load = 450 N, Effort = 150 N, VR = 4. Find efficiency.
 Answer: MA = 450 / 150 = 3; η = (3 / 4) × 100 = 75%.

 

Q17. A pulley system has VR = 6, lifts load 720 N with 150 N effort. Find efficiency.
 Answer: MA = 720 / 150 = 4.8; η = (4.8 / 6) × 100 = 80%.

 

Q18. Effort arm = 1.2 m, Load arm = 0.4 m, Load = 300 N. Find effort (ideal).
 Answer: VR = 1.2 / 0.4 = 3; Effort = Load / VR = 300 / 3 = 100 N.

 

Q19. VR = 5, η = 90%, Load = 450 N. Find effort.
 Answer: MA = 0.9 × 5 = 4.5; Effort = 450 / 4.5 = 100 N.

 

Q20. Load = 800 N, Effort = 200 N, VR = 5. Find efficiency.
 Answer: MA = 800 / 200 = 4; η = (4 / 5) × 100 = 80%.

 

Q21. A block and tackle with 4 strands lifts 480 N. Find effort (ideal).
 Answer: VR = 4; Effort = 480 / 4 = 120 N.

 

Q22. A machine has MA = 2, VR = 4. Find efficiency.
 Answer: η = (2 / 4) × 100 = 50%.

 

Q23. Load = 900 N, Effort = 300 N, VR = 4. Find efficiency.
 Answer: MA = 900 / 300 = 3; η = (3 / 4) × 100 = 75%.

 

Q24. Effort arm = 1.8 m, Load arm = 0.6 m, Load = 600 N. Find effort.
 Answer: VR = 1.8 / 0.6 = 3; Effort = 600 / 3 = 200 N.

 

Q25. VR = 4, MA = 3.6. Find efficiency.
 Answer: η = (3.6 / 4) × 100 = 90%.

 

Q26. VR = 6, η = 75%. Load = 900 N. Find effort.
 Answer: MA = 0.75 × 6 = 4.5; Effort = 900 / 4.5 = 200 N.

 

Q27. VR = 3, Effort = 150 N, η = 80%. Find load.
 Answer: MA = 0.8 × 3 = 2.4; Load = 2.4 × 150 = 360 N.

 

Q28. Load = 500 N, VR = 4, Effort = 200 N. Find efficiency.
 Answer: MA = 500 / 200 = 2.5; η = (2.5 / 4) × 100 = 62.5%.

 

Q29. Load = 720 N, Effort = 240 N, VR = 4. Find efficiency.
 Answer: MA = 3; η = (3 / 4) × 100 = 75%.

 

Q30. Effort arm = 2 m, Load arm = 1 m, Effort = 200 N. Find load (ideal).
 Answer: VR = 2 / 1 = 2; Load = 200 × 2 = 400 N.

 

Q31. VR = 5, MA = 4.2. Find efficiency.
 Answer: η = (4.2 / 5) × 100 = 84%.

 

Q32. Load = 600 N, Effort = 150 N, VR = 6. Find efficiency.
 Answer: MA = 4; η = (4 / 6) × 100 = 66.7%.

 

Q33. VR = 3, η = 70%. Load = 420 N. Find effort.
 Answer: MA = 0.7 × 3 = 2.1; Effort = 420 / 2.1 = 200 N.

 

Q34. VR = 2, η = 80%, Effort = 50 N. Find load.
 Answer: MA = 0.8 × 2 = 1.6; Load = 1.6 × 50 = 80 N.

 

Q35. VR = 4, Effort = 60 N, η = 75%. Find load.
 Answer: MA = 0.75 × 4 = 3; Load = 3 × 60 = 180 N.

 

Q36. Load = 200 N, VR = 2, Effort = 120 N. Find efficiency.
 Answer: MA = 200 / 120 = 1.67; η = (1.67 / 2) × 100 = 83.5%.

 

Q37. VR = 5, η = 100%. Effort = 50 N. Find load.
 Answer: MA = 5; Load = 5 × 50 = 250 N.

 

Q38. VR = 4, η = 50%. Load = 400 N. Find effort.
 Answer: MA = 0.5 × 4 = 2; Effort = 400 / 2 = 200 N.

 

Q39. Load = 900 N, VR = 6, η = 90%. Find effort.
 Answer: MA = 0.9 × 6 = 5.4; Effort = 900 / 5.4 = 166.7 N.

 

Q40. VR = 3, Load = 180 N, Effort = 80 N. Find efficiency.
 Answer: MA = 180 / 80 = 2.25; η = (2.25 / 3) × 100 = 75%.

 

Q41. VR = 2, MA = 1.5. Find efficiency.
 Answer: η = (1.5 / 2) × 100 = 75%.

 

Q42. Effort arm = 1.5 m, Load arm = 0.3 m, Load = 600 N. Find effort (ideal).
 Answer: VR = 1.5 / 0.3 = 5; Effort = 600 / 5 = 120 N.

 

Q43. VR = 6, MA = 5.4. Find efficiency.
 Answer: η = (5.4 / 6) × 100 = 90%.

 

Q44. Load = 700 N, VR = 7, Effort = 120 N. Find efficiency.
 Answer: MA = 700 / 120 ≈ 5.83; η = (5.83 / 7) × 100 ≈ 83.3%.

 

Q45. VR = 4, Load = 400 N, η = 75%. Find effort.
 Answer: MA = 0.75 × 4 = 3; Effort = 400 / 3 ≈ 133.3 N.

 

Q46. VR = 2, Load = 150 N, Effort = 100 N. Find efficiency.
 Answer: MA = 1.5; η = (1.5 / 2) × 100 = 75%.

 

Q47. VR = 5, Load = 500 N, η = 80%. Find effort.
 Answer: MA = 0.8 × 5 = 4; Effort = 500 / 4 = 125 N.

 

Q48. VR = 3, Load = 270 N, Effort = 120 N. Find efficiency.
 Answer: MA = 2.25; η = (2.25 / 3) × 100 = 75%.

 

Q49. VR = 4, η = 100%. Effort = 25 N. Find load.
 Answer: MA = 4; Load = 4 × 25 = 100 N.

 

Q50. VR = 6, η = 70%, Load = 420 N. Find effort.
 Answer: MA = 0.7 × 6 = 4.2; Effort = 420 / 4.2 = 100 N.

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