How to find decceleration of the car

[vastandfurious]

Hello,
I have a question to figure out that asks for the final decceleration of the car, if the coefficient between the road and tire is 0.7 and the guy in the car pushes the breaks causing the tire to deccelearate at 2 m/s...hmmm...It is a simple question, but I cannot figure out if the friction increases the deceleration or decreases it...Any help is appreciated...

EDIT: BTW just noticed, that I can't post homework questions here...my bad

 

[Hootenanny]

Welcome to PF,

It is a simple question, but I cannot figure out if the friction increases the deceleration or decreases it

all you need to do is ask yourself, does the frictional force oppose or promote the motion of the car? What does friction do?

-Hoot