# Kinetic friction

1. Feb 27, 2013

### mels

1. The problem statement, all variables and given/known data

A car is moving with a speed of 20m/s when the brakes are applied. The wheels lock (stop spinning). After travelling 40m, the car stops. Determine the coefficient of kinetic friction between the tires and the road.

2. Relevant equations

Fk=uk x Fn

3. The attempt at a solution

I dont know how to encorporate the given into the equation !
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Feb 27, 2013

### Platformance

There's another equation you need, one that puts all the given data together.

3. Feb 27, 2013

### raghav singh

You can apply simple formula...

calculate the acceleration 'a'... by
(square of final velocity)-(square of initial velocity)=2x a x distance

a=20x20/(2x40)
a=5

balance the force
uk x mass x g = mass x a
uk=a/g
uk=5/10=0.5

Last edited by a moderator: Feb 28, 2013
4. Feb 28, 2013

### mels

okay thank you ! i really appreciate it :)