A 50kg girl is swinging on a swing from rest. Then, the power delivered when moving with a velocity of 2m/s upwards in a direction making an angle 60∘ with the vertical is
A
980W
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B
490W
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C
490√3W
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D
245W
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Solution
The correct option is C490√3W Two force are acting on bob, tension and weight. Power of tension will be zero and that of weight is,
P = mgv cos(90∘+θ) P = mgv cos(90∘+60∘) =−mgv. sin60∘ =−50×9.8×2×√32=−490√3W ∴ Power delivered is 490√3W