The ceiling of a hall is 40m high. For maximum horizontal distance, the angle at which the ball may be thrown with a speed of `56ms^(-1)` without hitting the ceiling of the hall is

Options

A. `25^(@)`
B. `30^(@)`
C. `45^(@)`
D. `60^(@)`

Answer

B

Explanation

Here, `u = 56 ms^(-1)`
Let `theta` be the angle of projection with the horizontal to have maximum range, with maximum height = 40 m
Maximum height, `H = (u^(2) sin^(2) theta)/(2g)`
` 40 = ((56)^(2) sin^(2) theta)/(2 xx 9.8)`
`sin^(2) theta = (2xx 9.8 xx 40)/((56)^(2)) = (1)/(4) or sin theta = (1)/(2) = sin^(-1) ((1)/(2)) = 30^(@)`