A bullet moving with a speed of `150ms^-1` strikes a tree and penetrates 3.5 cm before stopping. What is the magnitude of its retardation in the tree and the time taken for it to shop after striking the tree?

Explanation

Velocity of the bullet, `u=150 m//s`,
Final velocity, v=0
Distance travelled, s=3.5 cm =`3.5 times 10^-2 m`
a) Accleration, `a=(v^2-u^2)/(2s)`
`=(0^2-150^2)/(2times3.50times10^-2)`
`=22500/(7times10^-2)`
`=-3.214 times10^5m//sec^2`
(-ve sign for retardation)
b) Time taken to stop, `t=(v-u)/a`
`=(-150)/(-3.214 times10^5)`
`=4.67 times10^-4 sec`.