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JEE Main & Advanced Physics NLM, Friction, Circular Motion Question Bank Second Law of Motion

  • question_answer
    A body of mass 2 kg moving on a horizontal surface with an initial velocity of 4 m/sec comes to rest after 2 sec. If one wants to keep this body moving on the same surface with a velocity of 4 m/sec, the force required is            [NCERT 1977]

    A)                         8 N                 

    B)                         4 N            

    C)                         Zero                

    D)                         2 N

    Correct Answer: B

    Solution :

                                \[u=4\ m/s\], \[v=0,\ t=2\sec \]             \[v=u+at\] Þ \[0=4+2a\] Þ \[a=-2\,m/{{s}^{2}}\]             \[\therefore \] Retarding force\[=ma=2\times 2=4\]N This force opposes the motion. If the same amount of force is applied in forward direction, then the body will move with constant velocity.            


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