(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known dataCar A has a mass of 1900 kg and crashes into parked Car B with a mass of 1100 kg. Car A claims to have hit the brakes 15 metres before crashing into Car B. After the collision, Car A slid an additional 18 metres while pushing Car B 30 metres from its parked position. The coefficient of friction is .6 between the locked tires and the road. Prove that Car A was speeding. Legal speed limit of the road is 90 km/h.

2. Relevant equations

F=ma

W=[tex]\Delta[/tex]KE

KE=.5 x mv[tex]^{2}[/tex]

F[tex]_{net}[/tex]=F[tex]_{horizontal}[/tex]-F[tex]_{friction}[/tex]

F[tex]_{friction}[/tex]=[tex]\mu[/tex]mg

3. The attempt at a solution

I set force friction equal to the force of motion, and got that to be 11400 Newtons. Then I plugged that into the equation for work, and used 18m as the displacement, and 0 for the final velocity, and solved for the initial velocity. I got 14.697 m/s as that answer. Then I used the equation for work again, but this time I used 14.697 m/s as the final velocity, and found the initial velocity to be about 6 m/s. However, I don't think it's right, since I didn't use anything about Car B. I'm not sure exactly what to do with it.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Energy [Car collisions]

**Physics Forums | Science Articles, Homework Help, Discussion**