# If an object is moving at 15 m/s over a surface with a kinetic friction coefficient of u_k=225 /g, how much time will it take for the object to stop moving?

Mar 5, 2016

$= \frac{1}{15} s$

#### Explanation:

we know that frictional force acting on the body while moving in horizontal surface is given by
Kinetic friction ${F}_{k} = {\mu}_{k} m g$,where m= mass and g = acceleration due to gravity
So the retardation a$= {F}_{k} / m = \frac{{\mu}_{k} m g}{m} = {\mu}_{k} g = \frac{225}{g} \cdot g = 225 m {s}^{-} 2$

Initial velocity of the body $u = 15 m {s}^{-} 1$
Final velocity v = 0
If time required to stop be t then
$v = u - a t$
$\implies 0 = 15 - 225 t$
$\implies t = \frac{15}{225} s = \frac{1}{15} s$