7700-kg boxcar traveling 18m/s strikes a second car. The two stick together and move off with a speed of 5.0m/s. What is the mass of the second car?

Answer 1

Use the conservation of momentum equation to solve for the unknown M2.

M1*V1 + M2*V2 = (M1 + M2) Vfinal

V2 = 0 and Vfinal = 5.0 in this case, so

7700*18 = (7700 + M2)*5.0

Answer 2

20020