Question:
The $200 \mathrm{~m}$ free style women's swimming gold medal at Seol Olympic 1988 went to 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 $460 \mathrm{~W}$ to maintain her speed. Calculate the average force of resistance offered by the water during the swim.
Solution:
Power, $\mathrm{P}=\frac{\frac{1}{2}}{2} \mathrm{~V} / \mathrm{t}$
$W=P \times t=460 \times 117.56$
Also
$W=F \times d=F \times 200 \ldots \ldots(2)$
From 1 and 2
$F=(460 \times 117.56) / 200=270.3$
$F=270 \mathrm{~N}$