A horizontal bridge is built across a river. A student standing on the bridge throws a small ball vertically upwards with a velocity The ball strikes the water surface after . The height of the bridge above water surface is (Take ) [2023]

Question

A horizontal bridge is built across a river. A student standing on the bridge throws a small ball vertically upwards with a velocity $4 {ms}^{- 1} .$ The ball strikes the water surface after $4 s$ . The height of the bridge above water surface is (Take $g = 10 {ms}^{- 2}$ ) [2023]

Smart Achievers · Accepted Answer

(1)

Given, $u = 4 {ms}^{- 1}, v = 0, g = 10 {ms}^{- 2}$

Time taken by ball to reach its maximum height,

$v = u + a t$

$\Rightarrow 0 = 4 + (- 10) t or 4 = 10 t$

$t = 0.4 sec .$

The height of bridge above water surface is

$S = u t + \frac{1}{2} a t^{2} \Rightarrow S = (0) t + \frac{1}{2} (10) {(3.6)}^{2}$

$S = 64 m$

Solution

Q.
A horizontal bridge is built across a river. A student standing on the bridge throws a small ball vertically upwards with a velocity $4 {ms}^{- 1} .$ The ball strikes the water surface after $4 s$ . The height of the bridge above water surface is (Take $g = 10 {ms}^{- 2}$ ) [2023]

1 64 m

2 68 m

3 56 m

4 60 m

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