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16. A boy takes 3 minutes to lift a 20 litre water bucketfrom a 20 m deep well, while his father does it in2 minutes. (a) Compare : (i) the work, and (ii) powerdeveloped by them. (b) How much work eachdoes ? Take density of water = 103 kg m-andg= 9.8 N kg- |
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Answer» Answer: Volume of water = 20 L = 20/1000= 0.02 m^3 Mass of water = Density × Volume = 10^3×0.02 = 20 KG (i) Work done by BOY = mgh = 20×9.8×20 = 3920J Work done by father = mgh = 20×9.8×20=3920J Compare work done => 3920 : 3920 = 1:1 (ii) Time taken by boy = 3 MIN = 180 s Time taken by father = 2 min = 120 s Power developed by the boy = Work done /Time = 3920/180 Power developed by the father = Work done /Time = 3920/120 Comparing power devolped => 3920/180 : 3920/120 =2:3 |
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