A girl of mass $50 \mathrm{~kg}$ swinging on a cradle. If she moves with a velocity of $2 \mathrm{~ms}^{-1}$…

A girl of mass $50 \mathrm{~kg}$ swinging on a cradle. If she moves with a velocity of $2 \mathrm{~ms}^{-1}$ upwards in a direction making an angle $60^{\circ}$ with the vertical, then the power generated is $\left(\mathrm{g}=9.8 \mathrm{~ms}^{-2}\right)$
  1. $245 \mathrm{~W}$
  2. $490 \sqrt{2} \mathrm{~W}$
  3. $490 \sqrt{3} \mathrm{~W}$
  4. $980 \mathrm{~W}$

Solution


$\begin{aligned} & P=\vec{F} \cdot \vec{V} \quad=m g v \cos 150^{\circ} \\ & =50 \times 9.8 \times 2 \cos 150^{\circ} \quad=-490 \sqrt{3} \mathrm{w} \\ & P=490 \sqrt{3} \mathrm{watt}\end{aligned}$

Asked in: AP EAMCET 2017 (26 Apr Shift 1)

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