A particle of Q is projected from A at ground level. After 4 seconds the particle strikes the ground again at B where AB = 200m. Calculate the initial velocity of Q.

using A=theta

Equation 1

$\displaystyle 2usinA-2g=0$

$\displaystyle u=\frac{2g}{2sinA}$

Equation 2

$\displaystyle 4ucosA=200$

Sub 1 in 2

$\displaystyle 4*\frac{2g}{2sinA}cosA=200$

$\displaystyle tanA=\frac{8g}{400}$

then $\displaystyle A=11.1$

and $\displaystyle u=50.95ms^{-1}$

is everything correct?

thanks for your help!