The potential energy of a projectile at its highest point is`3/4` of the value of its initial kinetic energy. Therefore its angle of projection is ..........

Options

A. `45^(@)`
B. `30^(@)`
C. `75^(@)`
D. `60^(@)`

Answer

D

Explanation

`U= k_(0) - (3)/(4) k_(0) = (1)/(4) k_(0)`
At max height U = K
`K= K_(0) cos ^(2) theta `
`(1)/(4) K_(0) = k_(0) cos^(2) theta`
`:. , (1)/(4) =cos^(92) theta`
`:. , (1)/(2) = cos theta`
`:. , theta cos ^(-1) ((1)/(2))`
`theta = 60^(@)`