A body is dropped from the roof of a multistoried building it passes the ceiling of the 15th storey at a speed of `20ms^(-1)` if the height of each storey is 4m, the number of stereys in the building is `(takeg=10ms^(-2)` and neglect air resistance)

Options

A. 20
B. 25
C. 30
D. 35

Answer

A

Explanation

Distance traveled when it gains velocity of `20 m//s`
`v^(2)-0=2gh,h=(v^(2))/(2g)=(400)/(20)=20m`
Number of stories`=(20)/(4)=5`
Total no of stories `15+5=20`