If a projectile is fired with an initial velocity u at an angle θ from the horizontal, for what time does it remain in the air?
Vertical component of initial velocity, uy=u sinθ
At the highest point, vertical component of velocity will become zero.
From the first equation of motion, v=u+at⇒0=uy−gt⇒0=u sinθ−gt⇒t=usinθg
∴ Time of flight, T=2t=2u sin θg