Championship swimmers take about \(22 \mathrm{~s}\) and about 30 arm strokes to move through the water in a \(50 \mathrm{~m}\) freestyle NT race.

a. From Table 11.4, a swimmer's metabolic power is \(800 \mathrm{~W}\). If the efficiency for swimming is \(25 \%\), how much energy is expended moving through the water in a \(50 \mathrm{~m}\) race?

b. If half the energy is used in arm motion and half in leg motion, what is the energy expenditure per arm stroke?

c. Model the swimmer's hand as a paddle. During one arm stroke, the paddle moves halfway around a \(90-\mathrm{cm}\)-radius circle. If all the swimmer's forward propulsion during an arm stroke comes from the hand pushing on the water and none from the arm (somewhat of an oversimplification), what is the average force of the hand on the water?

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TABLE 11.4 Metabolic power use during activities Activity Metabolic power (W) of 68 kg individual Typing 125 Ballroom dancing 250 Walking at 5 km/h 380 Cycling at 15 km/h 480 Swimming at a fast 800 crawl Running at 15 km/h 1150