# Homework Help: Calulate Acceleration from Friction

1. Oct 13, 2008

### halo9909

1. The problem statement, all variables and given/known data
What would be the size and direction of the acceleration of the car? Why would it be constant?

The coefficient of sliding friction between rubber tires and wet pavement is 0.50. The brakes are applied to a 710-kg car traveling 20 m/s, and the car skids to a stop.

So
m=710kg
vi=20
vf=0
Coefficient Slideing friction=.50
a=
2. Relevant equations

to get the Ff= .50 * 710kg * -9.8 = -3479

3. The attempt at a solution
I have calulated the Force of the friction that the road exerts on the car which is -3479N

From here how wouldyou go about ot calculate the acceleration? since ou do not have dispalcement or time

2. Oct 13, 2008

### nicksauce

Remember, F=ma, so a = F/m. You have F and you have m. The velocity information seems superfluous here.

3. Oct 13, 2008

### halo9909

Negative signs can make a little error, I had 4.9 instead of -4.9 the whole the

never really thought of a=F/m i just plug all of them into the F=ma in the base form