A bullet moving with a velocity of `30sqrt(2) ms^(-1)` is fired into a fixed target. It penetrated into the target to the extent of s metres. If the same bullet is fired into a target of thickness `(s)/(2)` metres and of the same material with the same velocity, then the bullet comes out of the target with velocity

Options

A. `20 ms^(-1)`
B. `30 ms^(-1)`
C. `20sqrt(2)ms^(-1)`
D. `10sqrt(2)ms^(-1)`

Answer

B

Explanation

(b) Given, `u=30 sqrt(2)ms^(-1)`
Distance=sm
Let a be the acceleration of the bullet
According to the first condition, (v=0)
Given, `v^(2)=u^(2)-2as`
`0=900xx2-2as`
`implies a=(900)/(s) ms^(-2)`
For second condition,
`v^(2)=u^(2)-2as=(30sqrt(2))^(2)-2xx(900)/(s)xx(s)/(2)`
`implies v^(2)=1800-900 implies v=sqrt(900)=30ms^(-1)`