1. The problem statement, all variables and given/known data A 1200 kg car drives headlong into a brick wall at 14 m/s and rebound at 3 m/s. The collision lasts for .10 seconds. What is the average force on the car during the collision? 2. Relevant equations F=ma f*change in time= mass * change in velocity f= mass*change in velocity / change in time 3. The attempt at a solution I got the change in velocity to be 17 m/s. I did 14 m/s - (-3m/s) = 17 (I put the 3 as negative since it it rebounding it is going in the negative x direction. f= 1200(17)/ .1 = 204,000. this is wrong..where am I messing up?