A boy is swinging on a swing such that his lowest and highest position are at heights of $2 m$ and $4.5 m$ respectively. His velocity at the lowest position is

2.5 m s^{- 1}

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7 m s^{- 1}

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14 m s^{- 1}

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20 m s^{- 1}

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Solution

The correct option is B $7 m s^{- 1}$
The height at which the swing comes from its highest position is

$h = 4.5 - 2$

Work done=change in kinetic energy

$m g h = \frac{1}{2} m v^{2}$

By substituting the values in the above equation we get

$v = \sqrt{2 g h}$

$v = \sqrt{2 \times 10 \times 2.5}$

$v = 7 m / s$

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A boy is swinging on a swing such that his lowest and highest position are at heights of 2m and 4.5m respectively. His velocity at the lowest position is

The correct option is B 7ms−1The height at which the swing comes from its highest position is h=4.5−2 Work done=change in kinetic energy mgh=12mv2 By substituting the values in the above equation we get v=√2gh v=√2×10×2.5 v=7m/s

A boy is swinging on a swing such that his lowest and highest position are at heights of $2 m$ and $4.5 m$ respectively. His velocity at the lowest position is