In CID serial (on TV), Abhijeet fires a bullet of mass 100 g with a speed of `100ms^(-1)` on a soft polywood of thickness 4 cm the buttle oemerges with `10%` of its initial KE. Find the emergent speed of the bullet.

Explanation

`"Initial KE of the bullet "=(1)/(2)m u^(2)=(1)/(2)xx(100)/(1000)xx100xx100=500 J`
`"Final KE of the bullet "=(10)/(100)xx500=50J`
Let emergent speed of the bullet be `v, (1)/(2)mv^(2)=50`
`rArr v=sqrt((2xx50)/((100)/(1000)))=31.6ms^(-1)`