Bicyclists in the Tour de France do enormous amounts of work during a race. For
ID: 1448402 • Letter: B
Question
Bicyclists in the Tour de France do enormous amounts of work during a race. For example, the average power per kilogram generated by seven-time-winner Lance Armstrong (m = 75.0 kg) is 6.50 W per kilogram of his body mass. (a) How much work does he do during a 105-km race in which his average speed is 14.5 m/s? J (b) Often, the work done is expressed in nutritional Calories rather than in joules. Express the work done in part (a) in terms of nutritional Calories, noting that 1 joule = 2.389 10-4 nutritional Calories. nutritional Calories
Explanation / Answer
A.
Power = (6.5 W/kg)* 75 kg = 487.5 W
He covers 105 km race at speed of 14.5 m/sec
thus
time = 105000/14.5 = 7241.37 sec
Now
Power = work/time
work = power*time
W = 487.5*7241.37
W = 3.53*10^6 J
B.
1 joule = 2.389*10^-4 calories
W = 3.53*10^6 J = 3.53*10^6*2.389*10^-4
W = 843.317 Nutiritional calories
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