Assertion: Frictional forces are conservative forces.& from Class Physics Laws of Motion

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NEET Physics : Laws of Motion

Multiple Choice Questions

91.

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



92.

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



93.

The force of gravitation is

  • repulsive

  • conservative

  • electrostatic

  • non-conservative



94.

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



95.

Assertion: Frictional forces are conservative forces. 

Reason:  Potential energy can be associated with frictional forces.

  • 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



96.

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



97.

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



98.

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.



99.

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



100.

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.



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