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%
c. 86%
b. 23%
d. 100%
A
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