WAEC Physics 2012 Paper

Concept:The time of flight is the total time a projectile remains in the air, which depends on the vertical component of its initial velocity.Explanation:The vertical component of the initial velocity is $U\sin\theta$.At maximum height, the vertical velocity becomes zero.Using $v = U\sin\theta - gt$, time to reach maximum height is $t = \frac{U\sin\theta}{g}$.The upward and downward journeys take equal times.Therefore, total time of flight is $T = 2t = \frac{2U\sin\theta}{g}$.Answer:C. $\frac{2U\sin\theta}{g}$