Author Question: A railroad freight car, mass 15 000 kg, is allowed to coast along a level track at a speed of 3.0 ... (Read 59 times)

jeatrice · **on:** Jul 28, 2018

A railroad freight car, mass 15 000 kg, is allowed to coast along a level track at a speed of 3.0 m/s. It collides and couples with a 54 000-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. 78
b. 22
c. 18
d. 38
e. 14

Question 2

A 22.3-g bullet moving at 1 000 m/s is fired through a one-kg block of wood emerging at a speed of 100 m/s. What is the change in the kinetic energy of the bullet-block system as a result of the collision assuming the block is free to move?
a. 0 J
b. 10.8 kJ
c. 10.8 kJ
d. 11.2 J
e. 223 J