Q 11-03-050JEE MainJEE Main 2026 (24 Jan, Shift 1)Easy
A boy throws a ball into air at $45^\circ$ from the horizontal to land it on a roof of a building of height $H$. If the ball attains maximum height in 2 s and lands on the building in 3 s after launch, then value of $H$ is ______ m.
$(\text{g} = 10\ \text{m/s}^2)$
Answer: (D) 15
Time to reach maximum height: $t = \dfrac{u_y}{g} = 2$ s, so $u_y = 20$ m/s.
Height at $t = 3$ s (the ball is coming down onto the roof):
$$H = u_yt - \frac12gt^2 = 20(3) - 5(9) = 15\ \text{m}$$
Solution by Sreeraj P, M.Sc Physics