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NCERT Solutions for class 11 Physics | Chapter 6 - Work, Energy and Power

(1) When a Cylinder Filled With Gas is Fitted With a Movable Piston is Allowed to Expand, Then the Work Done by the Gas is Positive. Identify the Statement True or False?
[A] True
[B] False
Answer: True
(2) The Work Done by the Centripetal Force for a Body Moving in a Circular Path is __________?
[A] Negative
[B] Zero
[C] Constant
[D] Positive
Answer: Zero

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(3) When a Working Coolie Walks on a Horizontal Platform Having a Load on His Head, the Work Done by Him on the Load is Zero. Identify the Statement True or False?
[A] False
[B] True
Answer: True
(4) A Gardener Pushes a Lawn Roller Via a Distance of 20m. If He Applies a Force of 20kg Weight in a Direction Inclined at 60° to the Ground, Then What Will Be the Work Done by Him? (g=9.8m/s2)
[A] 400J
[B] 1960J
[C] 250J
[D] 2514J
Answer: 1960J
(5) The Bullet That Has Fired from a Gun Can Pierce a Target Due to Its __________?
[A] Heat energy
[B] Mechanical energy
[C] Acceleration
[D] Kinetic energy
Answer: Kinetic energy
(6) A truck and car are moving with same Kinetic energies on a straight road.Their engines are simuktanously switched off .Which one will stop at a lesser distance
[A] Truck
[B] Car
[C] Both will stop at the same distance
[D] Cannot say with the given data
Answer: Truck
(7) A body of mass 1 kg is rotating in a circular path of radius 1 m with constant velocity of 5 rev/sec. The work done in one complete revolution is
[A] 5 J
[B] 2.5 J
[C] 12.5 J
[D] 0
Answer: 0
(8) A loaf of Bread gives a boy of mass 40kg an energy of 21kJ. If the efficiency is 28% then the height can be climbed by him using this energy is
[A] 15 m
[B] 21 m
[C] 19.5m
[D] 15.5 m
Answer: 15 m
(9) If the velocity of the object is increased by 0.1%, then the kinetic energy is increased by
[A] 0.1 %
[B] 0.2%
[C] 0.4%
[D] 0.01%
Answer: 0.2%
(10) What is the smallest unit of power?
[A] Watt
[B] Kilowatt
[C] Horse power
[D] Milliwatt
Answer: Watt
(11) A body is falling freely under the action of gravity alone in vacuum.Which of the following quantities remain constant during the fall?
[A] Kinetic energy.
[B] Potential energy.
[C] Total mechanical energy.
[D] Total linear momentum.
Answer: Total mechanical energy.
(12) A body of mass 1 kg travels with a velocity of 10 m/s , this a wall and rebounds . If 50% of its initial energy is wasted as heat , its kinetic energy at the instant of rebounding is
[A] 20 J
[B] 60 J
[C] 50 J
[D] 25 J
Answer: 25 J
(13) A miner hauls up a load equal to his own weight from 50 meters depth upto the surface of the mine . The amount of work done by him is
[A] twice the work he dose in lifting himself up
[B] half the work he dose in lifting himself up
[C] Zero
[D] equal to the work he dose in lifting himself up
Answer: twice the work he dose in lifting himself up
(14) A body of mass 100 kg falls from a height of 10 m . Its increase in kinetic energy is
[A] 9800 J
[B] 1000 J
[C] 5000 J
[D] 3000 J
Answer: 9800 J
(15) Consider the following two statements A : Linear momentum of a system of particles is zero B : Kinetic energy of a system of particles is zero . Then
[A] A implies B and B implies A .
[B] A implies B but B dose not imply A .
[C] A dose not imply B but B implies A .
[D] A dose not imply B and B dose not imply A .
Answer: A dose not imply B but B implies A .
(16) A quantity of work of 1000 J is done in 2 seconds . The power utilised is
[A] 998 W
[B] 1002 W
[C] 2000 W
[D] 500 W
Answer: 500 W
(17) 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
Answer: 3.6 J
(18) A small spherical ball is gently dropped from the rim of a hemispherical bowl with a smooth surface . The ball will
[A] rise up to the opposite rim of the bowl after reaching the bottom
[B] stop at the bottom of the bowl
[C] rise halfway up the bowl after reaching the bottom
[D] shoot out of the bowl through the opposite rim of the bowl
Answer: rise up to the opposite rim of the bowl after reaching the bottom
(19) A body of mass m moving with a velocity of 10 m/s makes an elastic collision with another body of same mass initially at rest . The first body comes at rest after the collision . Then the second mass will travel with a velocity of
[A] 10 m/s
[B] 5 m/s
[C] 20 m/s
[D] 15 m/s
Answer: 10 m/s
(20) During inelastic collision between two bodies, which of the following quantities always remain conserved?
[A] Total kinetic energy.
[B] Total mechanical energy.
[C] Total linear momentum.
[D] Speed of each body
Answer: Total linear momentum.

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