In a ballistics demonstration a police officer fires a bullet of mass 50 g with speed 200 ms-1 on soft plywood of thickness 2 cm. The bullet emerges with only 10% of its initial kinetic energy. The emergent speed of the bullet is reduced by.
1
68.4% of the initial speed.
2
90% of the initial speed.
3
31.6% of the initial speed.
4
10% of the initial speed.