1. The problem statement, all variables and given/known data A car of mass 1500kg is parked on a 30degree slope before rolling down a distance of 30m onto a flat section where it collides with a stationary car. The cars stick together and scrape along the road for 20m until they come to a rest. Calculate the velocity of the two combined cars immediately after the collision. Calculate the energy lost in the collision and the average coefficient of dynamic friction between the road and the two vehicles 2. Relevant equations 3. The attempt at a solution Pythagoras gives that the first car will drop a vertical height of 15m. So mgh=0.5mv^2 energy conservation for the first car when it reaches the bottom of the slope. So it's velocity at the bottom of the slope will be 17.15m/s Then to find the velocity of the combined cars immediately after the collision I need to use conservation of momentum BUT I don't have the mass of the second car?? m1v1 +m2v2 = (m1+m2) v3 1500 * 17.15 + m2 *0 = (1500 +m2) * v3 How can I find the resultant velocity??