A projectile is thrown in the upward direction making an angle of 60o with the horizontal direction with a velocity of 150 ms-1. Then the time after which its inclination withthe horizontal is 45o is

At the two points of the trajectory during projectile motion, the horizontal component of the velocity is same. Then150×12=v×12  or  v=1502ms−1 Initially: uy=usin⁡60∘=15032ms−1 Finally: vy=vsin⁡45∘=1502×12=1502ms−1 But vy=uy+ayt  or  1502=15032−10t     10t=1502(3−1)  or  t=7.5(3−1)