Question

Two projectiles are thrown with the same initial velocity, one at an angle and the other at an angle of . (a) Can both projectiles strike the ground at the same distance from the projection point? (b) Can both projectiles be in air for the same time interval? 

Answer 1

time of flight for a projectile = 2usin($\theta$ )/ g

so if a projectile is thrown at an angle theta then time of flight = 2usin($θ$) / g and if it thrown at an angle (90 - $θ$ ) then time of flight = 2usin(90-thta) / g = 2ucos(thta) / g ; so clearly in the two cases the time of flight differs.

Therefore, considering initial velocity, both projectiles will strike the ground same time.