Question

A 1000 kg car is moving with a constant speed. It is being pushed with 3000 N of force. Find the coefficient of kinetic friction, k. (Hint: You should find the acceleration of the car first so you can find the net force).

Answer 1

The acceleration of the car can be given as,

`a=(F)/(m)`

Plug in the known values,

`\begin{gathered} a=\frac{3000\text{ N}}{1000\text{ kg}}(\frac{1kgm/s^2}{1\text{ N}})_{} \\ =3m/s^2 \end{gathered}`

The net force which acts on the car is,

`F=ma`

The frictional force acting on the car is,

`f=\mu_kmg`

The net force is balanced by the frictional force which can be solved as,

`\begin{gathered} \mu_kmg=ma \\ \mu_k=(a)/(g) \end{gathered}`

Substitute the known values,

`\begin{gathered} \mu_k=(3m/s^2)/(9.8m/s^2) \\ =0.306 \end{gathered}`

Thus, the coefficient of kinetic friction is 0.306.