A projectile is thrown with velocity 𝑣 making an angle θ with the horizontal. It just crosses the tops of two poles, each of height ℎ, after 1s and 3s respectively. The time of flight of the projectile is

A projectile is thrown with velocity 𝑣 making an angle θ with the horizontal. It just crosses the tops of two poles, each of height ℎ, after 1s and 3s respectively. The time of flight of the projectile is

Question : A projectile is thrown with velocity 𝑣 making an angle θ with the horizontal. It just crosses the tops of two poles, each of height ℎ, after 1s and 3s respectively. The time of flight of the projectile is