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..

 

[thomate1]

I would first clarify the context of this problem. Is the car in motion or at rest? Is the acceleration due to an external force or is it caused by the frictional force itself? These details are important in determining the appropriate equation to use to solve for the frictional force.

If the car is in motion and the acceleration is due to an external force, then the frictional force can be found by subtracting the net force (Fnet) from the force of gravity (Fg). This would give us the following equation:

Ff = Fg - Fnet

Ff = (925 kg)(9.8 m/s^2) - (925 kg)(-12.2 m/s^2)

Ff = 9065 N + 11285 N

Ff = 20350 N

If the car is at rest and the acceleration is caused by the frictional force, then we can use the equation Ff = μFnorm, where μ is the coefficient of friction and Fnorm is the normal force. However, without knowing the coefficient of friction or the normal force, we cannot solve for the frictional force in this case.

Therefore, in order to fully solve this problem, we need more information about the context and the forces acting on the car. I would suggest reviewing the given information and clarifying any missing details before proceeding with the solution.