A person $A$ of $50 k g$ rests on a swing of length $1 m$ making an angle $37^{o}$ with the vertical. Another person $B$ pushes him to swing on other side at $53^{o}$ with vertical. The work done by person $B$ : $[g = 10 m / s^{2}]$

50 J

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9.8 J

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100 J

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10 J

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Solution

The correct option is C $100 J$
Formulae,

$h cos θ_{1} = 1 \times cos 37 = 1 \times \frac{4}{5} = \frac{4}{5} m$

$h cos θ_{2} = 1 \times cos 53 = 1 \times \frac{3}{5} = \frac{3}{5} m$

$h = h cos 37 - h cos 53 = \frac{4}{5} - \frac{3}{5} = \frac{1}{5}$

$W = m g h$

$= 50 \times 10 \times \frac{1}{5} = 100 J$

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