Question

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.

Answer 1

$$\begin{gathered} \mathrm{Time}\mathrm{taken}\mathrm{to}\mathrm{cover}200\mathrm{m},t=1\min 57.56\mathrm{seconds}=117.56\mathrm{s} \\ \mathrm{Power}\mathrm{exerted}\mathrm{by}\mathrm{her}, \\ P=460\mathrm{W} \\ P=\frac{\mathrm{W}}{t} \\ \mathrm{Work}done,\mathrm{W}=Pt=460\times 117.56\mathrm{J} \\ \mathrm{Again},\mathit{}W=Fs \\ \Rightarrow F=\frac{W}{\mathrm{s}} \\ =\frac{460\times 117.56}{200} \\ =270.3\mathrm{N}\approx 270\mathrm{N} \end{gathered}$$

∴ Resistance force offered by the water during the swim is 270 N.