Find frictional force from mass and acceleration

[liz777]

Homework Statement

Acceleration of a car is -12.2 m/s/s. The car has a mass of 925 kg. Find the frictional force.

The Attempt at a Solution

So A=-12.2, M=925 kg

Fnet=MA
=925(-12.2)
= -11285 N

Fg=mg
=925(9.8)
=9065 N

Since there is no vertical direction, Fg=Fnorm.

Now I have the equation Ff(frictional force= coefficient(normal force)

I'm really stuck here. I need to know the Fa or the coefficient to solve?

 

[glueball8]

If that's the whole questions then Fnet=Ff=ma

so you got it..