Worksheet Solutions: Machines | Physics Class 10 ICSE PDF Download

A. Multiple Choice Questions

Q1. Which quantity tells how many times a machine multiplies the effort force?

• (a) Velocity Ratio

• (b) Mechanical Advantage

• (c) Efficiency

• (d) Work Output
  Answer: (b) Mechanical Advantage
  Explanation: Mechanical Advantage (MA) = Load ÷ Effort. It shows the force multiplication.

Q2. Velocity Ratio (VR) of a machine is defined as:

• (a) Load ÷ Effort

• (b) Work Output ÷ Work Input

• (c) Displacement of effort ÷ Displacement of load

• (d) Effort ÷ Load
  Answer: (c) Displacement of effort ÷ Displacement of load
  Explanation: VR compares how far the effort point moves to how far the load moves in the same time.

Q3. An ideal machine has efficiency equal to:

• (a) 0%

• (b) 50%

• (c) 75%

• (d) 100%
  Answer: (d) 100%
  Explanation: In an ideal machine, there is no energy loss; work input equals work output.

Q4. In which class of lever is the effort between the fulcrum and the load?

• (a) Class I

• (b) Class II

• (c) Class III

• (d) None of these
  Answer: (c) Class III
  Explanation: Class III: Fulcrum — Effort — Load (gives speed gain, MA < 1).

Q5. A single movable pulley (ideal) is used to lift a 100 N load. The effort required is:

• (a) 100 N

• (b) 75 N

• (c) 50 N

• (d) 25 N
  Answer: (c) 50 N
  Explanation: For a single movable pulley, MA = 2. Effort = Load ÷ MA = 100 ÷ 2 = 50 N.

B. Short Answer Questions

Q1. A lever has an effort arm of 60 centimetres and a load arm of 20 centimetres. Find the Mechanical Advantage and say whether it is a force multiplier.
Answer: Mechanical Advantage = 3; Yes, it is a force multiplier.
Solution: Mechanical Advantage = Effort arm ÷ Load arm = 60 ÷ 20 = 3. Since it is greater than 1, the lever multiplies force.

Q2. A machine lifts a 240 newton load by applying an effort of 80 newton. If its Velocity Ratio is 4, find (a) the Mechanical Advantage, (b) the efficiency.
Answer: (a) Mechanical Advantage = 3 (b) Efficiency = 75%
Solution:

1. Mechanical Advantage = Load ÷ Effort = 240 ÷ 80 = 3

2. Efficiency = Mechanical Advantage ÷ Velocity Ratio = 3 ÷ 4 = 0.75 = 75%

Q3. What does a single fixed pulley do? State its Mechanical Advantage, Velocity Ratio and its main use.
Answer: It changes the direction of effort. Mechanical Advantage = 1, Velocity Ratio = 1.
Solution: With a fixed pulley, the load and effort are equal in ideal conditions (so no force gain) and both move the same distance. Its main use is to make lifting convenient by changing the direction of effort (pull down to lift up).

Q4. Identify the class of lever when the load lies between the fulcrum and the effort. Give two examples and state whether its Mechanical Advantage is greater than 1 or less than 1.
Answer: Class II lever; examples: wheelbarrow, nutcracker; Mechanical Advantage is greater than 1.
Solution: Class II lever arrangement: Fulcrum — Load — Effort. The effort arm is longer than the load arm, so the lever multiplies force.

Q5. A block-and-tackle system has 4 strands of rope supporting the load (ideal). If the load is 200 newton, find (a) the Mechanical Advantage and the Velocity Ratio, (b) the effort needed, (c) how far the effort moves when the load rises by 0.5 metre.
Answer: (a) Mechanical Advantage = 4, Velocity Ratio = 4 (b) Effort = 50 newton (c) Effort distance = 2.0 metres
Solution:

1. For n supporting strands, ideal Mechanical Advantage = Velocity Ratio = n = 4

2. Effort = Load ÷ Mechanical Advantage = 200 ÷ 4 = 50 newton

3. Velocity Ratio = Effort distance ÷ Load distance → Effort distance = 4 × 0.5 = 2.0 metres

C. Long Answer Questions

Q11. A machine lifts a 300 newton load through 2 metres while the effort point moves 6 metres. The effort used is 120 newton. Find (a) the Mechanical Advantage, (b) the Velocity Ratio, (c) the efficiency, (d) the work input and work output.
Answer: Mechanical Advantage = 2.5; Velocity Ratio = 3; Efficiency ≈ 83.33%; Work input = 720 joules; Work output = 600 joules
Solution (stepwise):

1. Mechanical Advantage = Load ÷ Effort = 300 ÷ 120 = 2.5

2. Velocity Ratio = Displacement of effort ÷ Displacement of load = 6 ÷ 2 = 3

3. Efficiency = Mechanical Advantage ÷ Velocity Ratio = 2.5 ÷ 3 = 0.8333 = 83.33%

4. Work input = Effort × Effort distance = 120 × 6 = 720 joules

5. Work output = Load × Load distance = 300 × 2 = 600 joules

6. Check: Efficiency = Work output ÷ Work input = 600 ÷ 720 = 0.8333 (matches).

Q12.A wheelbarrow acts as a Class II lever. The distance from fulcrum (the wheel) to the load is 25 centimetres, and from fulcrum to the effort (handles) is 75 centimetres. The load is 180 newton. Find (a) the Mechanical Advantage, (b) the effort needed, (c) state whether this lever is a force multiplier and why.
Answer: (a) Mechanical Advantage = 3 (b) Effort = 60 newton (c) Yes, it is a force multiplier because the effort arm is longer than the load arm.
Solution (stepwise):

1. Mechanical Advantage = Effort arm ÷ Load arm = 75 ÷ 25 = 3

2. Effort = Load ÷ Mechanical Advantage = 180 ÷ 3 = 60 newton

3. Since Mechanical Advantage > 1, it multiplies force.

1. Single movable pulley gives Mechanical Advantage = 2 (the fixed pulley only changes direction).

2. Effort = Load ÷ Mechanical Advantage = 360 ÷ 2 = 180 newton

3. Velocity Ratio = 2, so Effort distance = Velocity Ratio × Load distance = 2 × 1.5 = 3.0 metres

4. Conclusion: You gain force by 2 times but must move the effort twice as far (trade-off between force and speed).