Question

4 ) A 1800-kg car is traveling at 20 m/s when it crashes into the rear end of a 1550-kg car traveling at 14 m/s in the same direction on ice. The two cars become stuck together and slide on the ice. How fast in m/s do the two cars move together immediately after the collision? Round your answer to 3 digits

Answer 1

Use conservation of momentum:

v = (m1 v1 + m2 v2) / (m1 + m2)
= (1800·20 + 1550·14) / (1800 + 1550)
= 57700 / 3350 = 17.2239... m/s

Rounded to three significant digits: 17.2 m/s.