A projectile is projected with velocity of 25 m s - 1 at an angle θ with the horizontal. After t seconds its inclination with horizontal becomes zero. If R represents horizontal range of the projectile, the value of θ will be : [use use g = 10 m s - 2 ]

Step-by-step solution

From the information given in the question, after time t the inclination of the projectile becomes zero i.e. the projectile is at the highest point. Therefore, t = T 2 = u sin θ g . The rang of the projectile R = 2 u 2 sin θ cos θ g . Now, R t 2 = 2 u 2 sin θ cos θ g × g 2 u 2 sin 2 θ = 2 g cot θ ⇒ θ = cot - 1 R 20 t 2