# Kinetic Energy/Forces problem

1. Oct 26, 2009

### kza62

1. The problem statement, all variables and given/known data
A car and driver weighing 5490 N passes a sign stating “Bridge Out 29.3 m Ahead.”
She slams on the brakes, and the car decelerates at a constant rate of 10.9 m/s2.
The acceleration of gravity is 9.8 m/s2 .
What is the magnitude of the work done stopping the car if the car just stops in time to avoid diving into the water?

2. Relevant equations
KE = 1/2mv^2
Ff = u * FN
FN = mg
F = ma

3. The attempt at a solution
Given:
a = -10.9
Fg = 9.8

need help in setting this problem up... i've never seen something weigh in N before is that important or relevant in any way? would I plug that into F = ma to find mass?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Oct 26, 2009

### rock.freak667

If the weight is 5490 N, can you find the mass of the person+car ?

If the deceleration is -10.9 m/s2 , can you get the force of friction acting on the car?

If you have the frictional force, can you find the work done by this force given the distance?