Work and Energy Test - Class 9

Multiple Choice Questions (15 marks)

Choose the correct option for each question.

1. The SI unit of work is:

a) Newton

b) Joule

c) Watt

d) Pascal

2. Which of the following is a form of energy?

a) Force

b) Power

c) Heat

d) Momentum

3. The work done by a force is zero when:

a) Force is perpendicular to displacement

b) Force is parallel to displacement

c) Displacement is zero

d) Both a and c

4. The kinetic energy of an object depends on:

a) Mass only

b) Velocity only

c) Both mass and velocity

d) Height from the ground

5. The potential energy of an object at a height is due to:

a) Its motion

b) Its position

c) Its temperature

d) Its charge

6. The SI unit of power is:

a) Joule

b) Watt

c) Newton

d) Pascal

7. When a body falls freely under gravity, its:

a) Kinetic energy increases

b) Potential energy increases

c) Total energy decreases

d) Total energy increases

8. The work-energy theorem states that:

a) Work done = Force × Distance

b) Work done = Change in kinetic energy

c) Energy can neither be created nor destroyed

d) Power = Work / Time

9. A person holding a bundle of books while standing still does:

a) Positive work

b) Negative work

c) Zero work

d) Maximum work

10. The commercial unit of energy is:

a) Joule

b) Watt

c) Kilowatt-hour

d) Newton

11. If the velocity of a body is doubled, its kinetic energy becomes:

a) Double

b) Half

c) Four times

d) One-fourth

12. The energy stored in a stretched spring is:

a) Kinetic energy

b) Potential energy

c) Heat energy

d) Chemical energy

13. The work done by gravity on a ball thrown vertically upwards is:

a) Positive

b) Negative

c) Zero

d) Cannot be determined

14. The law of conservation of energy states that:

a) Energy can be created

b) Energy can be destroyed

c) Energy can neither be created nor destroyed

d) Energy can be converted from one form to another

15. Power is defined as:

a) Work done × Time

b) Force × Distance

c) Work done / Time

d) Energy / Distance

Numerical Problems (15 marks)

Solve the following problems. Show your calculations.

1. Calculate the work done when a force of 15 N moves a body by 5 m. (Assume force and displacement are in the same direction)

2. A body of mass 2 kg is thrown vertically upwards with an initial velocity of 20 m/s. What will be its potential energy at the highest point? (g = 10 m/s²)

3. A man does 200 J of work in 10 s. What is his power?

4. A car of mass 1000 kg is moving with a velocity of 10 m/s. What is its kinetic energy?

5. A spring is compressed by 0.1 m. If the spring constant is 200 N/m, what is the potential energy stored in the spring?

Long Answer Questions (20 marks)

Answer the following questions in detail.

1. State and prove the work-energy theorem.

2. Differentiate between potential energy and kinetic energy with examples.

Results