In a ballistics demonstration, a police officer fires a bullet mass `50.0g` with speed `200ms^(-1)` on soft plywood of thickness 2.00cm. The bullet emerges only with `10%` of its initial kinetic energy. What is the emergent speed of the bullet ?

Explanation

The initial kinetic energy of the bullet is `mv^(2)/2= 1000J`. It has a final kinetic energy of `0.1 xx 1000 = 100J`. If `v_(f)` is the emergent speed of the bullet.
`1/2mv_(f)^(2) = 100J`
`v_(f) =sqrt(2xx100J)/(0.05kg)`
`=63.2ms^(-1)`.