Question

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. $\frac{v}{g}$

Answer 1

Answer: (A)

$\frac{v}{g\mu }$

Answer 2

Block $B$ will come to rest, if force applied to will vanish due to frictional force acting between block $B$ and surface, ie, force applied = frictional force
ie, $\mu m g=m a$
or $\mu m g=m\left(\frac{v}{t}\right)$
or $t=\frac{v}{\mu g}$