Question

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?

Answer 1

`=1/15s`

Explanation:

we know that frictional force acting on the body while moving in horizontal surface is given by
Kinetic friction `F_k=mu_kmg`,where m= mass and g = acceleration due to gravity
So the retardation a`=F_k/m =(mu_kmg)/m=mu_kg=225/g*g=225 ms^-2`

Initial velocity of the body `u =15ms^-1`
Final velocity v = 0
If time required to stop be t then
`v=u-at`
`=>0=15-225t`
`=>t=15/225s=1/15s`