# Homework Help: Auto crash problem

1. Nov 11, 2007

### gfrant7070

1. The problem statement, all variables and given/known data

Skid marks at auto accidents are used to reconstruct traffic accidents. In this particular scenario, a truck of mass 1750kg moving with a velocity of (22m/s, 90 degrees) collided with a sports car of mass 1025 kg moving with an unknown velocity. After the collision, the vehicles stuck together and moved off at an angle of 138 degrees with respect to east (0 degrees). The skid marks are 57m long. If the coefficient of kinetic friction is determined to be .37, what was the velocity of the sports car at the time of the collision? Assume there is level ground at the location of the collision.

3. The attempt at a solution

N/A, I'm stuck on step 1

Any help is appreciated guys, thanks!

2. Nov 11, 2007

### Dick

Step 1 is to find an applicable equation. And it's tough to get stuck there. Think about conservation of momentum.

3. Nov 11, 2007

### gfrant7070

Yeah; through a series of unfortunate events I lost my textbook :( I know there is a somewhat simple equation, but I just don't know what it is. I googled around, but nothing came up. If someone can post the equation for me I can try and just go from there.

4. Nov 11, 2007

### Dick

Momentum is conserved. Momentum is m*v. So m1*v1+m2*v2=m3*v3. Be warned that the v's are vectors. BTW, that's not the sort of equation you should really have to memorize. It's more of a concept than an equation.