I don't know how to approach the problem below: An SUV and a car collide at a stoplight. The wreck slides to a complete stop. mass SUV = 4200 kg mass car = 2100 kg velocity car = 0 m/s distance the wreck slides = 12 meters Mu = .65 Find the velocity of the SUV. What I tried: Since it crash is shown as being completely inelastic I know that both objects have the same velocity after the crash so I can treat their mass as one also. First I set up an equation for the momentum: p1 + p2 = p1 (prime) + p2 (prime) [mass SUV * velocity SUV] + [mass car + velocity car] = vprime [mass SUV + mass car] [4200 * velocity SUV] + 0 = 6300v(prime) So from that equation I have two unknowns. I know that the final velocity of the wreck is 0 and that the initial velocity before the slide is the same as Vprime. The full body diagram that I drew for the wreck just before the slide has four forces acting upon the mass: Fg down, Fn up, the momentum to the right, and friction to the left. After doing that I'm not sure where to go next. Any ideas?