The trajectory of a projectile projected from origin is given by the equation `y = x - (2x^(2))/(5)` .The initial velocity of the projectile is

Options

A. `25 ms^(-1)`
B. `2 //5 ms^(-1)`
C. `5 //2ms^(-1)`
D. `5 ms^(-1)`

Answer

D

Explanation

`y= ax - bx ^2 , as a=I= tan theta implies theta = 45^@ `
` b=2/5 =(g)/(2v^2 cos^2 theta)`
` U^2 = (5 g)/( 4 cos ^2 theta)`
` U^2 = ( 5g )/( 4 cos 45^@ ) = (5g)/(2) = 2.5 g = 25 m//s`