A horizontal bridge is built across a river. A student standing on the bridge throws a small ball vertically upwards with a velocity <math> <mn>4</mn> <msup> <mrow> <mrow> <mtext> </mtext> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">s</mi> </mrow> </mrow> <mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </mrow> </msup> </math> . The ball strikes the water surface after <math> <mn>4</mn> <mtext> </mtext> <mi mathvariant="normal">s</mi> </math> . The height of bridge above water surface is (Take <math> <mi mathvariant="normal">g</mi> <mo>=</mo> </math> <math> <mn>10</mn> <msup> <mrow> <mrow> <mtext> </mtext> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">s</mi> </mrow> </mrow> <mrow> <mrow> <mo>-</mo> <mn>2</mn> </mrow> </mrow> </msup> </math> ):

Let height of bridge = h <!- [endif]-><!- [endif]->Displacement of ball, S = - h <!- [endif]-><!- [endif]-> S = u t + 1 2 a t 2 - h = 4 × 4 + 1 2 ( - 10 ) ( 4 ) 2 ⇒ h = 64 m <!- [endif]-><!- [endif]->

A horizontal bridge is built across a river. A student standing on the bridge throws a small ball vertically upwards with a velocity <math> <mn>4</mn> <msup> <mrow> <mrow> <mtext> </mtext> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">s</mi> </mrow> </mrow> <mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </mrow> </msup> </math> . The ball strikes the water surface after <math> <mn>4</mn> <mtext> </mtext> <mi mathvariant="normal">s</mi> </math> . The height of bridge above water surface is (Take <math> <mi mathvariant="normal">g</mi> <mo>=</mo> </math> <math> <mn>10</mn> <msup> <mrow> <mrow> <mtext> </mtext> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">s</mi> </mrow> </mrow> <mrow> <mrow> <mo>-</mo> <mn>2</mn> </mrow> </mrow> </msup> </math> &nbsp;): &lt;!-- [if !supportLineBreakNewLine]--&gt; &lt;!--[endif]--&gt;

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Physics Class 11th Physics Motion in Straight Line

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

Option 1 -

$68 m$

Option 2 -

$56 m$

Option 3 -

^{$60 m$}

Option 4 -

$64 m$

2 Views | Posted 3 weeks ago

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1 Answer

Answered by

Raj Pandey | Contributor-Level 9

3 weeks ago

Correct Option - 4

Detailed Solution:

Let height of bridge $= h$

Displacement of ball, $S = - h$

$\begin{array}{r} S = u t + \frac{1}{2} {a t}^{2} \\ - h = 4 \times 4 + \frac{1}{2} (- 10) (4)^{2} \\ \Rightarrow h = 64 m \end{array}$

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

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A horizontal bridge is built across a river. A student standing on the bridge throws a small ball vertically upwards with a velocity 4 m s - 1 . The ball strikes the water surface after 4 s . The height of bridge above water surface is (Take g = 10 m s - 2 ):

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