A 10-g bullet moving horizontally with a speed of 2.0 km/s strikes and passes through a 4.0-kg block moving with a speed of 4.2 m/s in the opposite direction on a horizontal frictionless surface. If the block is brought to rest by the collision, what is the kinetic energy of the bullet as it emerges from the block?
1) 0.51 kJ
2) 0.29 kJ
3) 0.80 kJ
4) 0.13 kJ
5) 20 kJ
Answer: 1