1.

The potential energy of a projectile at its highest point is3/4 of the value of its initial kinetic energy. Therefore its angle of projection is ..........

Answer»

`45^(@)`
`30^(@)`
`75^(@)`
`60^(@)`

Solution :`U= k_(0) - (3)/(4) k_(0)= (1)/(4) k_(0)`
AtmaxheightU = 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`
`:. , thetacos ^(-1)((1)/(2))`
`theta= 60^(@)`


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