Question

If an object is moving at `20 m/s` over a surface with a kinetic friction coefficient of `u_k=3/g`, how much time will it take for the object to stop moving?

Answer 1

`t=20 s`

Explanation:

`F_f=k*m*g`
`F_f=3/cancel(g)*m*cancel(g)`
`F_f=m`
`F=m*a" The Newton's law"`
`m=m*a`
`a=1 m/s^2`
`v_l :"last velocity ; "v_i:" initial velocity"`
`v_l=v_i-a*t`
`v_l=0 " when object is stops"`
`0=20-1*t`
`t=20 s`