Inelastic Collision with Friction and angle

[Geowarrior77]

Suppose the traffic investigators determined from the skid marks that these cars came to rest with a displacement of 9.72m at 72 degrees North of East, and the coefficient of friction was .72. The red car had a mass of 1000kg, but the blue car's mass was 1300 kg in this accident. Find the velocities (in mph) of each car immediately before their collision.

Solution: I used two formulas that I read in another forum but we have never been taught the first one in class. First I used ( Vf2-Vo2=-2UkgD) then M1V1i+M2V2i=(M1+M2)Vf

D=9.72
Theta=72 degrees
Uk=.72
M1=1000kg
M2=1300kg

1000kg*Vi+1300kg*0=(2300kg)(11.71m/s)
=26.93m/s=60.3mph

1000kg*0+1300kg*Vi=(2300kg)(11.71m/s)
=20.72m/s=46.4mph

I got 60.3 mph for the Red Car and 46.4 mph for the Blue Car. Any idea if that is the correct way to go about this problem.

 

[LightHero]

Yes, that is the correct way to go about this problem. You used the correct formulas and your calculations are correct.