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Homework Help: Linear momentum and its Conservation

  1. Apr 13, 2009 #1
    1. The problem statement, all variables and given/known data
    The subject lies on a horizontal pallet floating on a film of air. Friction on the pallet is negligible. Initially, the momentum of the system is zero. When the heart beats, it expels a mass m of blood into the aorta with speed v, and the body and platform move in the opposite direction with speed V. The speed of the blood can be determined independently (for example, by observing an ultrasound Doppler shift). Assume that the blood's speed is 54.0 cm/s in one typical trial. The mass of the subject plus the pallet is 54.0 kg. The pallet moves 6.55x10^-5 m in 0.160 s after one heartbeat. Calculate the mass of blood that leaves the heart

    2. Relevant equations
    p = mv

    3. The attempt at a solution
    I set found p=mv initial and final as well. I set initial and final momentum equal to each other and solved for mass of blood. However, my problem is I get a value of 23.4 kg which is intuitively impossible.
  2. jcsd
  3. Apr 13, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Show how you found that value.
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