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2 June, 03:52

Some runners train with parachutes that trail behind them to provide a large drag force. These parachutes are designed to have a large drag coefficient. One model expands to a square 1.8 m on a side, with a drag coefficient of 1.4. A runner completes a 200 m run at 5.0 m/s with this chute trailing behind. Part A How much thermal energy is added to the air by the drag force

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  1. 2 June, 04:06
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    13.9 kJ

    Explanation:

    Given that

    Length of the side, l = 1.8 m

    Drag coefficient, C (d) = 1.4

    Distance of run, d = 200 m

    Velocity of run, v = 5 m/s

    Density, ρ = 1.23

    Using the Aerodynamics Drag Force formula. We have

    F (d) = 1/2.ρ. A. C (d). v²

    The Area, A needed is 1.8 * 1.8 = 3.24 m². So that,

    F (d) = 1/2 * 1.23 * 3.24 * 1.4 * 5²

    F (d) = 139.482/2

    F (d) = 69.74

    recall that, energy =

    W = F * d

    W = 69.74 * 200

    W = 13948

    W = 13.9kJ

    Therefore, the thermal energy added to the air by the drag force is 13.9kJ
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