Estimate the energy required for an average person (see Fig. 9.32) to run a mile in 4 minutes in still standard air. Compare your estimate if you instead modeled the person as a cylinder \(6 \mathrm{ft}\) tall and \(2 \mathrm{ft}\) in diameter.

Fig. 9.32

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Shape Reference area Parachute Frontal area A-D Drag coefficient CD 1.4 Porosity 0 0.2 0.5 Porous Frontal area 1.42 1.20 0.82 parabolic dish A =D 0.95 0.90 0.80 Porosity = open area/total area Standing CDA = 9 ft Average Sitting CDA = 6 ft person Crouching CDA = 2.5 ft Fluttering flag A = (D 1723 CD 0.07 0.12 0.15 Empire State Building Frontal area 1.4 Frontal area 1.8 Six-car passenger train Bikes Upright commuter A = 5.5 ft 1.1 Racing A = 3.9 ft 0.88 Drafting A = 3.9 ft 0.50 Streamlined A = 5.0 ft 0.12 Tractor-trailer trucks Standard Frontal area 0.96 Fairing With fairing Frontal area 0.76 Gap seal With fairing and Frontal area 0.70 gap seal Tree U = 10 m/s U = 20 m/s U = 30 m/s Frontal area 0.43 0.26 0.20 Dolphin Wetted area Large birds Frontal area 0.0036 at Re = 6 x 106 (flat plate has CD = 0.0031) 0.40