A ball is projected from the ground at an angle θ with the horizontal. After 1 s it is moving at an angle 45 ° with the horizontal and after 2 s , it is moving horizontally. What is the velocity of projection of the ball?

Question

A ball is projected from the ground at an angle θ with the horizontal. After 1 s it is moving at an angle 45 ° with the horizontal and after 2 s , it is moving horizontally. What is the velocity of projection of the ball?, 10 3 m s - 1, 20 3 m s - 1, 10 5 m s - 1, 20 2 m s - 1

MARKS App · Accepted Answer

The ball will be vertical at the highest point so t u p = u s i n θ g = 2 ⇒ u s i n θ = 20 . . … … .(1) ∵ ta n α = u s i n θ - g t u c o s θ ⇒ 1 = 20 - g ( 1 ) u c o s θ ⇒ u c o s θ = 10 … . .(2) Squaring and adding equation (1) & equation (2), we get u s i n θ 2 + u cos θ 2 = 20 2 + 10 2 ⇒ u 2 = 500 ⇒ u = 10 5 m s - 1

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