From the top of tower, which is `19.6` m high, a blls in thrown horizonally. If the line joining the point of projection to the point where it hits the ground makes an angle of `45^(@)` with the horizontal, then the initial velocity of the ball is

Options

A. `9.8 ms^(-1)`
B. `4.9ms^(-1)`
C. `14.7ms^(-1)`
D. `2.8ms^(-1)`

Answer

A

Explanation

`tan 45^(@)=(H)/(x)=1`
`x=H=19.6`
time of flight `t=sqrt((2H)/(g))=sqrt((2xx19.6)/(9.8))=2` sec
`u=(x)/(t)=(19.6)/(2)=9.8m//s`