A Railroad Freight Car,mass 15,000 Kg,is Allowed to Coast Along

Multiple Choice

A railroad freight car,mass 15,000 kg,is allowed to coast along a level track at a speed of 2.0 m/s.It collides and couples with a 60,000-kg loaded second car,initially at rest and with brakes released.What percentage of the initial kinetic energy of the 15,000-kg car is preserved in the two-coupled cars after collision?

A) 20%
B) 23%
C) 86%
D) 100%