A boy throws a ball into air at 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 the value of H is _______ m. [2026]

Question

A boy throws a ball into air at $45 °$ 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 the value of H is _______ m. $(g = 10 {m/s}^{2})$ [2026]

Smart Achievers · Accepted Answer

(2)

$T = \frac{2 u_{y}}{g} = 4$

$\Rightarrow u_{y} = \frac{40}{2} = 20 m/s$

$y = u_{y} Δ t - \frac{1}{2} g {(Δ t)}^{2}$

$\Rightarrow H = 20 \times 3 - 5 \times 9$

$= 60 - 45$

$= 15 m$

Solution

Q.
A boy throws a ball into air at $45 °$ 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 the value of H is _______ m. $(g = 10 {m/s}^{2})$ [2026]

1 25

2 15

3 20

4 10

Ans.
(2)

$T = \frac{2 u_{y}}{g} = 4$

$\Rightarrow u_{y} = \frac{40}{2} = 20 m/s$

$y = u_{y} Δ t - \frac{1}{2} g {(Δ t)}^{2}$

$\Rightarrow H = 20 \times 3 - 5 \times 9$

$= 60 - 45$

$= 15 m$

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