5.36 - enhanced Problem 5.36 - Enhanced - with Feedback Running on a treadmill i

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5.36 - enhanced

Problem 5.36 - Enhanced - with Feedback Running on a treadmill is slightly easier than running outside because there is no drag force to work against. Suppose a 60 kg runner completes a 5.0 km race in 19 minutes You may want to review ( pages 143-144) Part A Determine the drag force on the runner during the race. Suppose that the cross section area of the runner is 0.72 m2 and the density of air is 1.2 kg/m3. Express your answer to two significant figures and include the appropriate units. D-Value Units Submit My Answers Give Up Incorrect; Try Again; no points deducted Enter your answer using dimensions of force Part B What is this force as a fraction of the runners weight? Express your answer using two significant figures 24 Submit My Answers Give Up

Explanation / Answer

(a)

average speed = 5000/(18*60) = 4.385 m/sec
drag force = V^2/1.6*A = 4.38^2/1.6*0.72 = 16.6 N
(b)

(drag force/runner weight) in % = 100*16.6/(60*9.8) = 2.82 %

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