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प्रश्न
The 200 m free-style women's swimming gold medal at Seoul Olympics in 1988 was won by Heike Friendrich of East Germany when she set a new Olympic record of 1 minute and 57⋅56 seconds. Assume that she covered most of the distance with a uniform speed and had to exert 460 W to maintain her speed. Calculate the average force of resistance offered by the water during the swim.
उत्तर
\[\text{ Time taken to cover 200 m, t } = 1 \min 57 . 56 \text{ seconds = 117 . 56 s } \]
\[\text{ Power exerted by her, } \]
\[\text{ P = 460 W } \]
\[P = \frac{W}{t}\]
\[\text{ Work done, W = Pt } = 460 \times 117 . 56 J\]
\[\text{ Again, W = Fs } \]
\[ \Rightarrow F = \frac{W}{s}\]
\[ = \frac{460 \times 117 . 56}{200}\]
\[ = 270 . 3 \text{ N } \approx 270 \text{ N } \]
∴ Resistance force offered by the water during the swim is 270 N.
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