# If a #11 kg# object moving at #15 ms^-1# slows down to a halt after moving #225 m,# what is the coefficient of kinetic friction of the surface that the object was moving over?

##### 1 Answer

#### Answer:

The coefficient of friction is related to the force acting on the object to accelerate (decelerate) it and the normal force:

#### Explanation:

First we need to calculate the acceleration (deceleration) of the object:

Now we have an acceleration and a mass and want to find a force... hmm, that sounds a lot like Newton's Second Law to me!

This is the actual magnitude of the frictional force. The coefficient of friction is defined as:

Then

Note that a frictional coefficient is a 'dimensionless' number which does not have units (because it is calculated as a force in