A 920-kg sports car collides into a rear end of a 2300 kg SUV stopped at a red light. The bumpers lock, the brakes are locked, and the two cars skid foward 2.8 m before stopping. The police officer, knowing that the coefficient of kinetic friction between tires and road is .80 , calculates the speed of the sports car at impact. What was that speed?(adsbygoogle = window.adsbygoogle || []).push({});

This is all that I did before I got stuck.

I set up the conservation of momentum :920 kg * V[tex]_{1}[/tex]= 3220 * V[tex]_2{}[/tex]

Then I did F[tex]\Delta[/tex]t= [tex]\Delta[/tex]P

I found the force to be 25244= 3220 V[tex]_{2}[/tex] / [tex]\Delta[/tex]t

Now is where I get stuck. I think I did something wrong because I'm pretty sure I need to do v/t =d.

Also not sure if I should use kinetic energy in this one since it's not conserved.

Any help will be great. Thanks as always.

On a side note: Isn't it hilarious how the officer knows the kinetic friction and calculates the speed.

**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!

# Homework Help: Inelastic Collisions

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