# If an object is moving at #120 m/s# over a surface with a kinetic friction coefficient of #u_k=12 /g#, how much time will it take for the object to stop moving?

##### 1 Answer

Oct 9, 2017

#### Answer:

The object will stop in 10 seconds. Complete solution follows...

#### Explanation:

We must start by determining the acceleration of the body, which we do by considering the force picture. Since the only horizontal force is friction, Newton's second law becomes

where

(if the motion is on a horizontal surface, it will be true that

Combining these two equations, we get

and, since we are told that

Now use the equation of motion

Since

so that