MCQ Questions for Class 11 Physics Chapter 6 Work Energy and Power

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MCQ Questions for Class 11 Physics Chapter 6 Work Energy and Power

Q.1. The magnitude of work done by a force
(a) depends on frame of reference
(b) does not depend on frame of reference
(c) cannot be calculated in non-inertial frames.
(d) both (a) and (b)

Answer Answer: (a)

Q.2. No work is done if
(a) displacement is zero
(b) force is zero
(c) force and displacement are mutually perpendicular
(d) All of these

Answer Answer: (d)

Q.3. When the force retards the motion of body, the work done is
(a) zero
(b) negative
(c) positive
(d) Positive or negative depending upon the magnitude of force and displacement

Answer Answer: (b)

Q.4. Work is always done on a body when
(a) a force acts on it
(b) it moves through a certain distance
(c) it experiences an increase in energy through a mechanical influence
(d) None of these

Answer Answer: (c)

Q.5. 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

Answer Answer: (a) When a person carrying load on his head moves over a horizontal road, work done against gravitational force is zero.

Q.6. In which of the following work is being not done?
(a) Shopping in the supermarket
(b) Standing with a basket of fruit on the head
(c) Climbing a tree
(d) Pushing a wheel barrow

Answer Answer: (b)

Q.7. 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) potential energy
(c) linear momentum
(d) angular momentum

Answer Answer: (a)

Q.8. If a light body and heavy body have same kinetic energy, then which one has greater linear momentum?
(a) Lighter body
(b) Heavier body
(c) Both have same momentum
(d) Can’t be predicted

Answer Answer: (b)

Q.9. The coefficient of restitution e for a perfectly inelastic collision is
(a) 1
(b) 0
(c) infinity
(d) –1

Answer Answer: (b) For a perfectly inelastic collision, e = 0.

Q.10. 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

Answer Answer: (a)

Q.11. The temperature at the bottom of a high water fall is higher than that at the top because
(a) by itself heat flows from higher to lower temperature
(b) the difference in height causes a difference in pressure
(c) thermal energy is transformed into mechanical energy
(d) mechanical energy is transformed into thermal energy.

Answer Answer: (d) By the principle of conservation energy

Q.12. A bullet is fired and gets embedded in block kept on table. If table is frictionless, then
(a) kinetic energy gets conserved
(b) potential energy gets conserved
(c) momentum gets conserved
(d) both (a) and (c)

Answer Answer: (c) Only momentum is conserved. Some kinetic energy is lost when bullet penetrates the block.

Q.13. A man pushes a wall and fails to displace it, he does
(a) negative work
(b) positive but not maximum work
(c) no work at all
(d) maximum positive work

Answer Answer: (c)

Q.14. Unit of energy is
(a) kwh
(b) joule
(c) electron volt
(d) All of these

Answer Answer: (d)

Q.15. Which of the following is not a conservative force?
(a) Gravitational force
(b) Frictional force
(c) Spring force
(d) None of these

Answer Answer: (b) As work done by frictional force over a closed path is not zero, therefore, it is non-conservative force.

Q.16. The speed of an object of mass m dropped from an inclined plane (frictionless), at the bottom of the plane, depends on:
(a) height of the plane above the ground
(b) angle of inclination of the plane
(c) mass of the object
(d) All of these

Answer Answer: (a)


Q.17. A particle is taken round a circle by application of force. The work done by the force is
(a) positive non–zero
(b) negative non–zero
(c) Zero
(d) None of the above

Answer Answer: (c)

Q.18. The coefficient of restitution e for a perfectly elastic collision is
(a) 1
(b) 0
(c) infinity
(d) –1

Answer Answer: (a)

Q.19. Four particles given, have same momentum. Which has maximum kinetic energy
(a) Proton
(b) Electron
(c) Deutron
(d) Alpha-particles

Answer Answer: (b)

Q.20. If two particles are brought near one another, the potential energy of the system will
(a) increase
(b) decrease
(c) remains the same
(d) equal to the K.E

Answer Answer: (a)

Q.21. When two spheres of equal masses undergo glancing elastic collision with one of them at rest, after collision they will move
(a) opposite to one another
(b) in the same direction
(c) together
(d) at right angle to each other

Answer Answer: (d) When two spheres of equal masses undergo a glancing elastic collision with one of them at rest, after the collision they will move at right angle to each other.

Q.22. In an inelastic collision
(a) momentum is not conserved
(b) momentum is conserved but kinetic energy is not conserved
(c) both momentum and kinetic energy are conserved
(d) neither momentum nor kinetic energy is conserved

Answer Answer: (b) Momentum is conserved but kinetic energy is not conserved.

Q.23. The potential energy of a system increases if work is done
(a) upon the system by a non conservative force
(b) by the system against a conservative force
(c) by the system against a non conservative force
(d) upon the system by a conservative force

Answer Answer: (d) When work is done upon a system by a conservative force then its potential energy increases.

Q.24. In an elastic collision, what is conserved ?
(a) Kinetic energy
(b) Momentum
(c) Both (a) and (b)
(d) Neither (a) nor (b)

Answer Answer: (c) In an elastic collision, momentum and K.E. both conserved.

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