A 10-g bullet moving horizontally with a speed of 1.8 km/s strikes and passes through a 5.0-kg block initially at rest on a horizontal frictionless surface. The bullet emerges from the block with a speed of 1.0 km/s. What is the kinetic energy of the block immediately after the bullet emerges?
1) 8.0 J
2) 6.4 J
3) 5.3 J
4) 9.4 J
5) 10 J
Answer: 2