When you ride a bicycle at constant speed, nearly all the energy you expend goes into the work you do against the drag force of the air. Model a cyclist as having cross-section area 0.40 m2 and, because the human body is not aerodynamically shaped, a drag coefficient of 0.90.

What is the cyclist's power output while riding at a steady 7.3 m/s?

Question

Kathleen Cowan

Physics

2 September, 02:58

When you ride a bicycle at constant speed, nearly all the energy you expend goes into the work you do against the drag force of the air. Model a cyclist as having cross-section area 0.40 m2 and, because the human body is not aerodynamically shaped, a drag coefficient of 0.90.

What is the cyclist's power output while riding at a steady 7.3 m/s?

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Answers (1)

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Sarahi Fields · Answer 1

Power output = 96.506 watts

Explanation:

Drag coefficient (Cd) = 0.9

V = 7.3 m/s

Air density (ρ) = 1.225 kg/m^ (3)

Area (A) = 0.45 m^2

Let's find the drag force;

Fd = (1/2) (Cd) (ρ) (A) (v^ (2))

So Fd = (1/2) (0.9) (1.225) (0.45) (7.3^ (2)) = 13.22N

Drag power = Drag Force x Drag velocity.

Thus drag power, = 13.22 x 7.3 = 96.506 watts