A ball is dropped from a height of `45 m` from the ground. The coefficient of restitution between the ball and the ground is `2/3`. What is the distance travelled by the ball in `4th` second of its motion. Assume negligible time is spent in rebounding. Let `g= 10 ms^(2)`

Options

A. `5m`
B. `20m`
C. `15m`
D. `10m`

Answer

C

Explanation

Time taken to fall through `45 m=sqrt((2xx45)/10)=3s`

`u_(1)=sqrt(2gh)=sqrt(2xx1xx45)=30m//s`
`u_(2)=eu_(1)=2/3xx30=20m//s`
Distance tavelled in the fourth second `= `distance travelled in `1s` after rebounding `20xx1-1/2xx10(1)^(2)=15m`