question_answer

A block B is pushed momentarily along a horizontal surface with an initial velocity v. If \[\mu \]is the coefficient of sliding friction between B and the surface, block B will come to rest after a time:

A) \[\frac{v}{g\mu }\]

B)  \[\frac{g\mu }{v}\]

C) \[\frac{g}{v}\]

D)  \[\frac{v}{g}\]

Correct Answer: A

Solution :

Block B will come to rest, if force applied to it will vanish due to frictional force acting between block B and surface, i.e., force applied = frictional force i.e., \[\mu mg=ma\,\,\Rightarrow a=\mu g\]? Now using \[v=u+at\] or \[0=v-\mu gt\Rightarrow t=\frac{v}{\mu g}\]