A railroad freight car coasts along a level track. It collides and couples with a second car, initially at rest and with brakes released. What percentage of the freight car's initial energy is preserved in the two-coupled cars after collision?

Question

A railroad freight car, mass 15972 #kg#, is allowed to coast along a level track at speed 2 #m/s#. It collides and couples with a 41386 #kg# loaded second car, initially at rest and with brakes released. What percentage of the initial kinetic energy of the 15972 #kg# car is preserved in the two-coupled cars after collision?

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Answer 1 · 2017-11-09T20:15:23

#m_1v_1=m_2v_2# Then, the initial Kinetic Energy is #U_{k1}=1/2m_1v_1^2# . Calculate #v_2# then plug that in to find #U_{k2}=1/2m_2v_2^2#.