Important Questions of Work, Energy and Power Physics | Zigya

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51.

A particle is displaced from a position 2i^ - j^ + k^ to another position 3i^ + 2j^ - 2k^ under the action of the force of 2i^ + j^ - k^. The work done by the force in an arbitrary unit is

  • 8

  • 10

  • 12

  • 16


52.

In elastic collision

  • both momentum and kinetic energies are conserved

  • both momentum and kinetic energies are not conserved

  • only energy is conserved

  • only mechanical energy is conserved


53.

A ball is released from the top of a tower. The ratio of work done by force of gravity in first, second and third second of the motion of the ball is

  • 1 : 2 : 3

  • 1 : 4 : 9

  • 1 : 3 : 5

  • 1 : 5 : 3


54.

When the kinetic energy of a body is doubled, its momentum increases by times

  • 2

  • 2

  • 4

  • 22


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55.

A body rolls down an inclined plane. If its kinetic energy of rotation is 40% of its kinetic energy of translation, then the body is

  • solid cylinder

  • solid sphere

  • disc

  • ring


56.

A 10 kg object collides with stationary 5 kg object and after collision they stick together and move forward with velocity 4 ms-1. What is the velocity with which the 10 kg object hit the second one ?

  • 4 ms-1

  • 6 ms-1

  • 10 ms-1

  • 12 ms-1


57.

When a force is applied on a moving body, its motion is retarded. Then the work done is

  • positive

  • negative

  • zero

  • positive and negative


58.

An α-particle of mass m suffers one dimensional elastic collision with a nucleus of unknown mass. After the collision the α-particle is scattered directly backwards losing 75% of its kinetic energy. Then the mass of the nucleus is

  • m

  • 2m

  • 3m

  • 32 m


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59.

An elastic ball is dropped from a height h and it rebounds many times from the floor. If the coefficient of restitution is e, the time interval between the second and the third impact, is

  • ev/g

  • e2v/g

  • e28hg

  • e2 hg


60.

An object of mass m is attached to light string which passess through a hollow tube. The object is set into rotation in a horizontal circle of radius, r1. If the string is pulled shortening the radius to r2, the ratio of new kinetic energy to the original kinetic energy is

  • r2r12

  • r1r22

  • r1r2

  • r2r1


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