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Homework Help: Swimmers and force

  1. Nov 21, 2007 #1
    1. The problem statement, all variables and given/known data
    Swimmers take about 22 seconds and about 30 arm strokes to move through the water in a 50 meter freestyle race.
    a. A swimmers metabolic rate is 800 watts. If the efficiency for swimming is 25%, how much energy is expended moving through the water in a 50 meter race.
    b. If half the energy is used in arm motion and half in leg motion, what is the energy expenditure per arm stroke?
    c. Model the swimmers hand as a paddle. During one armstroke the paddle moves halfway around a 0.90 meter radius circle. If all the swimmers forward propulsion during an arm stroke comes from the hand pushing on the water and none from the arm what is the average force of the hand on the water?

    2. Relevant equations
    efficiency= what you get/ what you pay
    delta E= P (delta t)
    p= F/A

    3. The attempt at a solution
    a. assuming i did this correctly
    what you get = 800 (0.25) = 200 W
    delta E= 200 (22 secs) = 4400Joules

    b. is not a problem as each arm stroke is approx 73.33 j/arm stroke

    c. i have no clue where to start
  2. jcsd
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