A particle is projected upwards with a velocity of 100 m/s at an angle of 60°, with the vertical. Then time taken by the particle when it will move perpendicular to its initial direction. Please explain and give answer.
Considering vertical motion we have:
(↑ +ve) u = 100cos60° => 100(1/2) = 50
a = -g = -10
When the velocity is perpendicular, the particle is going down and makes an angle of 30° with the vertical.