A drunken driver crashes his car into a parked car that has its brakes set. The two cars move off together (perfectly inelastic collision), with the locked wheels of the parked car leaving skid marks 6.0 m in length.

Question

If the mass of the moving car is 2130kg and the mass of the parked car is 1290 kg how fast was the first car travelling when it hit the parked car?
Assume that the driver of the moving car made no attempt to brake and that the coefficient of friction between the tires and the road is 0.18.

Answer 1

The momenum moving car=momenutum after.
2130*V=(2130+1290)Vf

Now, after the crash,
Vf^2=2 a d
where a=forcfriction/totalmass
= totalmass*g*.18/totalmass * d=.18g*d

vf^2=.18gd

solve for vf in that. then put in in the first equation above, solve for V, the velocity of the moving car beffore the crash. Check my thinking.

Answer 2

3.58m/s