Class 9 Physics: Work and Energy MCQ

Test your understanding of the concepts of work and energy with these multiple-choice questions. Each question is followed by its correct answer and a brief explanation.

1. Which of the following scalar quantity has the same unit as energy?

a) Force
b) Power
c) Momentum
d) Torque

Answer:

a) Force

Explanation:

Energy, work, and force all have the unit of joules (J) in the SI system. However, they represent different physical quantities.

2. The work done by a force acting on an object is zero if the force is:

a) Perpendicular to the direction of motion
b) In the same direction as the motion
c) In the opposite direction of the motion
d) Non-existent

Answer:

a) Perpendicular to the direction of motion

Explanation:

Work is calculated as the product of force and the displacement in the direction of the force. If the force is perpendicular to the direction of motion, the displacement in the direction of the force is zero, hence the work done is zero.

3. Potential energy is the energy possessed due to:

a) Motion
b) Heat
c) Position or configuration
d) Radiation

Answer:

c) Position or configuration

Explanation:

Potential energy is the energy an object has due to its position relative to other objects or due to its configuration.

4. What is the work done on an object moving in a circular path?

a) Maximum
b) Minimum
c) Zero
d) Infinite

Answer:

c) Zero

Explanation:

The force acting on an object moving in a circular path is perpendicular to the displacement at every point. Thus, the work done is zero.

5. In which of the following scenarios is no work done?

a) Pushing a wall
b) Lifting a book from the floor
c) Pulling a suitcase on a smooth floor
d) Dropping a ball

Answer:

a) Pushing a wall

Explanation:

Even though force is applied on the wall, there’s no displacement of the wall, thus the work done is zero.

6. The ability of a body to do work due to its motion is called:

a) Potential energy
b) Thermal energy
c) Kinetic energy
d) Chemical energy

Answer:

c) Kinetic energy

Explanation:

Kinetic energy is the energy a body has because of its motion.

7. The energy stored in a stretched rubber band is:

a) Kinetic energy
b) Thermal energy
c) Nuclear energy
d) Potential energy

Answer:

d) Potential energy

Explanation:

The stretched rubber band has energy due to its changed configuration, which is a form of potential energy.

8. A body at rest can have:

a) Kinetic energy
b) Momentum
c) Potential energy
d) None of the above

Answer:

c) Potential energy

Explanation:

A body at rest can have energy due to its position or configuration, which is potential energy.

9. Work is said to be done when:

a) Force is applied
b) Energy is transferred
c) Displacement occurs
d) Both force is applied and displacement occurs in the direction of the force

Answer:

d) Both force is applied and displacement occurs in the direction of the force

Explanation:

Work is done when there is a force causing a displacement in the direction of that force.

10. A machine that is 100% efficient:

a) Does not exist
b) Converts all input energy into work
c) Wastes no energy
d) Both b and c

Answer:

d) Both b and c

Explanation:

A 100% efficient machine would convert all input energy into useful work and would waste no energy.

11. Conservation of energy principle states that:

a) Energy can be created
b) Energy can be destroyed
c) Energy can neither be created nor destroyed, but can be transformed from one form to another
d) Energy is always constant

Answer:

c) Energy can neither be created nor destroyed, but can be transformed from one form to another

Explanation:

The principle of conservation of energy states that the total energy in an isolated system remains constant, though it can change forms.

12. When an apple falls from a tree, the kinetic energy of the apple increases because:

a) Its potential energy decreases
b) It gains speed
c) The gravitational force acts on it
d) Both a and b

Answer:

d) Both a and b

Explanation:

As the apple falls, it gains speed and its potential energy due to height decreases, converting into kinetic energy.

13. Work done by the gravitational force on a satellite moving around the Earth is:

a) Positive
b) Negative
c) Zero
d) Infinite

Answer:

c) Zero

Explanation:

The gravitational force acts towards the center of the Earth, and the displacement of the satellite is perpendicular to this force. Therefore, the work done is zero.

14. Which energy form is primarily used by plants for photosynthesis?

a) Kinetic energy
b) Thermal energy
c) Solar energy
d) Chemical energy

Answer:

c) Solar energy

Explanation:

Plants capture solar energy using chlorophyll in their cells and convert it into chemical energy through the process of photosynthesis.

15. If the speed of an object is halved, its kinetic energy will be:

a) Halved
b) Reduced to one-fourth
c) Doubled
d) Remain the same

Answer:

b) Reduced to one-fourth

Explanation:

Kinetic energy is given by the formula KE = 1/2 * m * v^2. If the speed (v) is halved, then the kinetic energy becomes proportional to the square of half the speed, which is one-fourth of the original energy.

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