Assertion: Animate object can accelerate in the absence of e

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 Multiple Choice QuestionsMultiple Choice Questions

191.

A ball of mass m is tied up with string and rotated along a horizontal circle of radius r. At an instant, its velocity is ν, and tension in string is T, the force required for circular motion is

  • T - m v2/2

  • T + m v2/2

  • m v2/r

  • zero


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192.

Assertion: Animate object can accelerate in the absence of external force. 

Reason:  Newton's second law is not applicable on animate object.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason is false.


A.

If both assertion and reason are true and reason is the correct explanation of assertion.

Animate object do not obey Newton's second law, so it can accelerate in the absence of external force.


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193.

A block of mass  m  is pulled along a horizontal surface by applying a force at an angle θ with the horizontal. If the block travels with a uniform velocity and has a displacement  d  and the coefficient of friction is  μ  then the work done by the applied force is

  • μ mg dcosθ + μ sinθ

  • μ mg d cosθcosθ + μ sinθ

  • μ mg d sinθcosθ + μ sinθ

  • μ mg d cosθcosθ - μ sinθ


194.

Assertion: A wheel moving down a perfectly frictionless inclined plane will undergo slipping (not rolling motion) 

Reason:  For perfect rolling motion, work done against friction is zero.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


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195.

A  ball  is  bouncing  down  a  flight of stairs. The  coefficient  of  restitution  is  e. The  height of  each  step  is  d  and  the  ball  descends one  step  each  bounce. After  each  bounce  it   rebounds  to  a  height h  above  the  next  lower  step. The  height  is  large  enough  compared  with  the  width of  step  so  that  the  impacts  are  effectively  head-on.  Find the  relationship  between  h  and  d.

  • h = d1 - e2

  • h = d1 + e2

  • h = d1 + e

  • h = d1 - e2


196.

Assertion:  Angular  speed  of  a  planet  around  the  sun  increases,  when  it  is  closer to the sun.

Reason: Total angular momentum of the system remains constant.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


197.

A particle of mass m moves with constant speed along a circular path of radius r under the action of force F. Its speed is

  • F rm

  • Fr

  • Fmr

  • Fm r


198.

A bullet is fired from a rifle and recoils. Kinetic energy of rifile is

  • less than K.E of bullet

  • greater than K.E of bullet

  • equal to K.E of bullet

  • none of the above


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199.

Figure shows the variation of energy with the orbit radius r of a satellite  in a circular motion. Mark the correct statement

              

  • C is total energy, B kinetic energy and A is potential energy.

  • A is kinetic energy, B total energy and C potential energy

  • A and 8 are the kinetic and potential energies and C the total energy of the satellite.

  • C and A arc kinetic and potential energy respectively and B the total energy of the satellite.


200.

The force of gravitation is

  • repulsive

  • conservative

  • electrostatic

  • non-conservative


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