8-18 In a race, a professional runner is keeping a constant velocity uphill. Pro

Question

8-18 In a race, a professional runner is keeping a constant velocity uphill. Professional athletes, like bicycle racers or runners, train to put out power. Even so, the maximum power output of a highly trained human is only about one-tenth of a horsepower.us tained Given: The runner has a mass of 68 kg. He is moving at a constant velocity of 3.7 m/s on a hill with a 12.1° incline, measured to the horizontal. One horsepower is 746 W. Find: (a) How much work does the runner do in s? (b) What is his power output in watts? (o) What is his power output in horsepower?

Explanation / Answer

Given , m = 68 kg , v = 3.7 m/s , angle (©) = 12.1°,

In time t = 1.0 s

Distance Travelled along the incline (d) = v*t

d = 3.7*1 = 3.7 m

Work done by runner (W) = mgsin(©)*d

W = 68*9.8*sin(12.1°)*3.7

W = 516.852 joules

b) power(P) = work /time = W/t

P = 516.852/1 = 516.852 watts

P = 516.852 watts

c) since 746 watts = 1 hp

P = (516.852/746)hp = 0.693 hp

P = 0.693 hp

Related Questions

Navigate

• Browse (All)
• Browse 8
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.