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23 October, 18:27

Calculate the energy in kcal used by a 55 kg woman who does 55 deep knee bends in which her center of mass is lowered and raised 0.400 m. (She does work in both directions.) You may assume her efficiency is 20%.

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  1. 23 October, 18:38
    0
    Answer: 0.57Kcal

    Explanation:

    Given m = 55kg, g = 9.8m/s²

    The Workdone is given by:

    W = mg∆h

    Where ∆h is the total distance covered

    ∆h = 55 * 0.4m = 22m

    W = 55 * 9.8 * 22

    W = 11,858 J

    Since 1Kilocalorie = 4,186.80Joules

    W = (11,858/4186.80) Kcal

    W = 2.8322Kcal

    But since her efficiency is 20%, (this means the conversion ratio between her chemical energy to mechanical; potential energy), the

    The efficient Energy used for the exercise is

    Ew = 0.20 * 2.8322

    Ew = 0.566 ~ = 0.57Kcal
  2. 23 October, 18:43
    0
    Energy = 1.132887kcal

    Explanation:

    Given

    Mass = 55kg

    Knee bend = 55

    Efficiency = 20%

    Displacement = 0.4m

    First, we'll calculate the total Workdone

    Work done = 2n (mgh)

    Where n = 55, m = 55kg, g = 9.8m/s² and h = 0.4m

    Work done = 2 * 55 * 55 * 9.8 * 0.4

    Work done = 23,716J

    Since the woman's efficiency is 20% of her total work done;

    Then,. her energy = 20% of 23,716J

    = 4,743.2

    = 4.74KJ

    Energy in kcal = 1.132887kcal
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