Question

Class 11 Physics MCQ Questions of Work, Energy and Power with Answers?

Answer 1

In general, the Class 11 Physics MCQ Questions of Work, Energy and Power with Answer are recognized as the most useful and widely applicable type of objective test elements. By preparing these MCQ Questions with Answers once after completing every topic, we are ready to attempt competitive exams easily and effectively.

These MCQ Questions for Class 11 Physics once after completing every topic, we are able to attempt the competitive exams like Board Exams, JEE Mains Exams, and NEET Exams easily and effectively. They could be used to measure the most important educational outcomes, such as understanding, knowledge, judgment, and problem-solving.

Let us go through the MCQ Questions for class 11 Physics work, power and energy with answers: – 

Practice MCQ Questions for class 11 Physics Chapter-Wise

1. A uniform chain of length 2 m is kept on a table such that a length of 60 cm hangs freely from the edge of the table. The total mass of the chain is 4 kg. What is the work done in pulling the entire chain on the table?

(a) 7.2 J
(b) 3.6 J
(c) 120 J
(d) 1200 J

2. When a work of 1 joule is done in 1 s, the power is:

(a) 1 W
(b) 1 KW
(c) 1 W/S
(d) 12 J

3. According to work-energy theorem, the work done by the net force on a particle is equal to the change in its

(a) kinetic energy
(b) angular momentum
(c) linear momentum
(d) potential energy

4. A light and a heavy body have equal momentum. Which one has greater K.E.?

(a) The lighter body
(b) The heavier body
(c) Both have equal K.E.
(d) Data given is incomplete

5. Kinetic energy, with any reference, must be

(a) positive
(b) zero
(c) negative
(d) None of these

6. The ...X... energy V(x) of the spring is said to be zero when block and spring system is in the ...Y... position. Here, X and Y refer to

(a) potential, equilibrium
(b) kinetic, equilibrium
(c) mechanical, equilibrium
(d) vibrational , left

7. Which of the following must be known in order to determine the power output of an automobile?

(a) Work performed and elapsed time of work
(b) Force exerted and distance of motion
(c) Mass and amount of work performed
(d) Final velocity and height

8. A vehicle is moving on a rough road in  a straight line with uniform velocity. Then

(a) no force is acting on the vehicle
(b) a force must act on the vehicle
(c) an acceleration is being produced in the vehicle
(d) no work is being done on the vehicle

9. A body projected vertically from the earth reaches a height equal to earth's radius before returning to the earth. The power exerted by the gravitational force is greatest

(a) at the instant just before the body hits the earth
(b) at the highest position of the body
(c) it remains constant all through
(d) at the instant just after the body is projected.

10. Assertion: When the force retards the motion of a body, the work done is zero.

Reason:  Work done depends on angle between force and displacement.

(a) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
(b) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
(c) Assertion is correct but Reason is incorrect
(d) Both Assertion and Reason are incorrect

11. When the force retards the motion of body, the work done is

(a) negative
(b) zero
(c) positive
(d) None of these

12. A man of 60 kg weight is standing at rest on a platform. He jumps up vertically a distance of 1 m and the platform at the same instant moves horizontally forward with the result that the man lands 1 meter behind the point on the platfrom from where the took the jump the total work done by the man at the instant he lands is

(a) 300 J
(b) 150 J
(c) 600 J
(d) zero

13. A body of mass 20 kg is initially at a height of 3 m above the ground. It is lifted to a height of 2 m from that position. Its increase in potential energy is

(a) 100 J
(b) 392 J
(c) 60 J
(d) -100 J

14. A man pushes a wall and fails to displace it, he does

(a) no work at all
(b) positive but not maximum work
(c) negative work
(d) maximum positive work

15. A boy carrying a box on his head is walking on a level road from one place to another is doing no work. This statement is

(a) correct
(b) incorrect
(c) partly correct
(d) cannot say

16. No work is done when:

(a) a nail is hammered into a wooden box
(b) a box is pushed along horizontal floor
(c) there is no component of force, parallel to the direction of motion
(d) none of these

17. A particle is taken round a circle by application of force. The work done by the force is

(a) Zero
(b) positive non–zero
(c) negative non–zero
(d) None of these

18. If a motorcyclist skids and stops after covering a distance of 15 m. The stopping force acting on the motorcycle by the road is 100 N, then the work done by the motorcycle on the road is

(a) Zero
(b) 750 J
(c) –1500 J
(d) 1500 J

19. A ball moves in a frictionless inclined table without slipping. The work done by the table surface on the ball is

(a) zero
(b) positive
(c) negative
(d) None of these

20. A boy pushes a toy box 2.0 m along the floor by means of a force of 10 N directed downward at an angle of 60° to the horizontal. The work done by the boy is

(a) 10 J
(b) 12 J
(c) 8 J
(d) 6 J

21. Two bodies of masses 1 kg and 5 kg are dropped gently from the top of a tower. At a point 20 cm from the ground, both the bodies will have the same 

(a) Momentum
(b) Kinetic energy
(c) Velocity
(d) Total energy

22. The potential energy of a body is given by, U = A – Bx² (Where x is the displacement). The magnitude of force acting on the particle is 

(a) Constant
(b) Proportional to x
(c) Proportional to x²
(d) Inversely proportional to x

23. Which one of the following is not a conservative force 

(a) Gravitational force
(b) Electrostatic force between two charges
(c) Electrostatic force between two charges
(d) Frictional force

24. Work done in raising a box depends on

(a) How fast it is raised
(b) The strength of the man
(c) The height by which it is raised
(d) None of the above

25. The force required to stretch a spring varies with the distance as shown in the figure. If the experiment is performed with the above spring of half length, the line OA will

(a) Shift towards F-axis
(b) Shift towards X-axis
(c) Remain as it is
(d) Become double in length

Answer 2

1. Answer: (b) 3.6 J

Explanation: Mass of the chain lying freely from the table = \(M\frac{1}{L}\)

\(=4kg\times\frac{0.6}{2}\)

= 1.2 kg

The distance of center of mass of chain from the table = \(\frac{1}{2}\times0.6m\) = 0.3 m

Thus the work done in pulling the chain = mgh = \(1.2\times10\times0.3J\) = 3.6 J

2. Answer: (a) 1 W

Explanation: One watt is defined as the energy consumption rate of one joule per second. 1W = 1J/1s.

3. Answer: (a) kinetic energy

Explanation: According to work-energy theorem, work done by a force in displacing a body on a horizontal level measures the change in its kinetic energy.

4. Answer: (a) The lighter body

Explanation: Since, momenta of heavy body and light body are same, thus velocity of light body is greater than that of heavy body. Also, kinetic energy is proportional to the square of velocity hence, lighter body has greater kinetic energy.

5. Answer: (a) positive

Explanation: Kinetic energy is equal to \(\frac{1}{2}\times mv^2\)

where v is velocity and its square is always positive.Therefore kinetic energy is always positive.

6. Answer: (a) potential, equilibrium

Explanation: The correct option for X is Potential and for Y is equilibrium, that is, The Potential energy of the spring is said to be zero when the block and spring system is in the equilibrium position.When the spring is extended to a displacement d, then the potential energy of the spring increases.

7. Answer: (a) Work performed and elapsed time of work

Explanation: Power is defined as the rate of doing work. For the automobile, the power output is the amount of work done (overcoming friction) divided by the length of time in which the work was done.

8. Answer: (b) a force must act on the vehicle

Explanation: Since the vehicle is moving with uniform velocity, thus its acceleration must be zero. The friction force exerted by the road on its tires equals the force provided by its engine. So, the acceleration of the vehicle is zero and thus the vehicle moves with uniform velocity.

9. Answer: (a) at the instant just before the body hits the earth

Explanation: P = F⋅V = FV cosθ. Power will be maximum when velocity and cosθ will be maximum.

10. Answer: (a) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Explanation: When the force retards the motion, the work done is negative.  Work done depends on the angle between force and displacement W = Fs cosθ.

11. Answer: (a) negative

Explanation: When the force retards the motion of a body, the work done is negative.

12. Answer: (c) 600 J

Explanation: W = mg \(\times\) d

W = 60 \(\times\) 10 \(\times\) 1

W = 600 J

13. Answer: (b) 392 J

Explanation: W = mgh 

= \(20\times9.8\times2\)

= 392 J

14. Answer: (a) no work at all

Explanation: As we know work done is Force X Displacement. If a person tries to push the wall he applies the force but displacement is zero, so product of force and displacement will be zero. So work done is zero.

15. Answer: (a) correct

Explanation: We know that the work done is product of the force and the displacement caused by the force on the body along the direction of the force. But here as the weight of the body is not causing any displacement, work done is zero.

16. Answer: (c) there is no component of force, parallel to the direction of motion

Explanation: The formula for work done when the force is applied at an angle to the direction of motion is given by,W = FS cosθ. When there will be no component of force, parallel to the direction of motion then force F in direction of motion is zero, so work done will also be zero.

17. Answer: (a) Zero

Explanation: Work done is zero in circular motion as the force acts on the centre of circular path and object move in direction of velocity making a perpendicular angle.

18. Answer: (a) Zero

Explanation: Through an equal and opposite force acts on the road but since road does not undergo any displacement, hence no work is done on the road.

19. Answer: (a) zero

Explanation: Angle between normal reaction N and displacement S is 90°.

∴W = 0

20. Answer: (a) 10 J

Explanation: W = Fs cosθ \(=10\times2\) cos 60°

= 10 J

21. Answer: (c) Velocity

Explanation: Velocity is same, because the gravitational acceleration on both of them possess the same velocity and free fall under the gravity is independent of the mass.

22. Answer: (b) Proportional to x

Explanation: Force on the particle = -dU/dx

⇒ F = 2BX

From the above equation: F \(\propto\) X

23. Answer: (d) Frictional force

Explanation: A conservative force is a force with the property that the total work done in moving a particle between two points is independent of the taken path. Equivalently, if a particle travels in a closed-loop, the total work done by a conservative force is zero. Examples:- Magnetic force, Electrostatic force, Gravitational force etc. Force of friction is not a conservative force since the work done by it depends on the path taken.

24. Answer: (c) The height by which it is raised

Explanation: Work done in raising a box on a platform depends on the height to which it is raised. When a body is raised to a height then work done is equal to the potential energy.

25. Answer: (a) Shift towards F-axis

Explanation: \(\therefore k\propto\frac{1}{L}\)

When the length of the spring is halved, its spring constant will become double.  Slope of the force displacement graph gives the spring constant (k)  of spring. If k becomes double then slope of the graph increases, i.e. Graph shifts towards force-axis. 

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