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. $g\mu /V$
• B. $g/V$
• C. $V/g$
• D. $V/(g\mu )$

Answer 1

Answer: (D)

Given $u=V$,
final velocity $=0$.
Using $v=u+at$
$\therefore 0=V-at$
or, $-a=\frac{0-V}{t}=-\frac{V}{t}$
$f=\mu R=\mu mg$
( $f$ is the force of friction)
$\therefore$ Retardation, $a=\mu g$
$\therefore t=\frac{V}{a}=\frac{V}{\mu g}$.