A lead bullet of mass 21g travelling at a speed of 100 `ms^(-1)` comes to rest in a wooden block. If no heat is taken away by the wood, the rise in temperature of the bullet in the wood nearly is (Sp. Heat of lead 80cal/kg `.^(@)C`)

Explanation

Kinetic energy of the bullet=heat gained by the
bullet, `(1)/(2)mv^(2)=mS Deltat`
`Deltat=(v^(2))/(2S)=((100)^(2))/(2xx0.03xx4.2xx1000)=39.68^(@)C`.