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Homework Help: Can you guys check these calculations for me

  1. May 27, 2013 #1
    Background Information:
    Clip Capacity of a Barret M82: 10 Rounds
    Mass of a .50 Cal Round: 46.7 grams = .0467 Kg
    Source: small arms by martin j. dougherty
    Average Muzzle Velocity of a Barret M82 .50 Cal Rifle: 853 m/s
    Average Specific heat capacity of normal human tissue: 3470 J/kg.C
    Average Specific heat capacity of Adipose tissue: 2348J/kg.C
    Source: http://www.itis.ethz.ch/itis-for-health/tissue-properties/database/heat-capacity/
    Weight of Blob: 976 lbs = 442.7 Kg

    Assumptions: Blob is around 75% adipose tissue(by weight) the remaining being normal body tissue. This means 332 Kg is adipose tissue. 110.6 Kg is other misc. body tissue.
    Important Formula:
    Kinetic Energy: Pe= ½mv2


    Ke= 1/2 (.0467 Kg)(853 m/s)2 = 16.98 Kj = 16980 J

    Joules needed to Raise blob 1 Degrees Celcius:
    (332 Kg * 2348 J/Kg) + (2348J/Kg * 110.6 Kg)= 779536J + 259688J= 1039224 J = 1039 Kj
    How much does Blob’s Temperature increase? : 19.98/ 1039 = .016 degrees Celcius
  2. jcsd
  3. May 27, 2013 #2


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    Science Advisor
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    Gold Member

    That should be "KE" not PE but otherwise looks ok.

    I made the KE of each round..

    = 0.5 * .0467 * 8532 = 16.9 kJ not 19.98 kJ

    There are 10 rounds so the energy is about 170 kJ.
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