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Homework Help: Temperature and pressure question

  1. Jan 5, 2006 #1
    hi everyone!

    I have the following problem:

    A volley-ball of mass m=200g and volume V=8L is inflated ith the overpresure of delta P = 0.2x10^5 Pa. A ball was thrown upwards to the height of h=20m, fell down, hit the ground, and bounced at approximately the same height. The temperature of the surrounding air is T=300k. the specific heat of the air is c=0.7kJ/(kg K)
    Estimate hte maximum temperature in the ball during the hit

    The problem i'm having:
    I don't understand what is overpressure in this context.. From what i've read on the web and the context of the question, i believe the delta P is how much over the atmospheric pressure..

    Also, i'm not really sure how to approach this question.. Can someone give me a hint of what to look up? thanks alot!
  2. jcsd
  3. Jan 6, 2006 #2
    Hi! I also think overpressure means the pressure over atmospheric pressure, in other words the net pressure that affects the ball.

    But I am somewhat fuzzy on exactly what should be done here, but I think the idea is that at some point during the bounce, all of the balls kinetic energy from the fall has trasnfered into its internal energy. Internal energy again is directly proportional to temperature, so you should get the change in temperature.
  4. Jan 6, 2006 #3
    Pressure = Overpressure + [tex]p_o[/tex] = 1 atm (101325 Pa)
    Pressure = [tex]p_o[/tex] (1 atm (101325 Pa)) - Underpressure

    If a bottle has the overpressure of 2,5 atm then it has a total pressure of 3,5 atm

    If a bottle has the underpressure of 0,25 atm then it has a total pressure of 0,75 atm
  5. Jan 6, 2006 #4
    After some more thinking, i figured that since the ball bounces and at one moment, it deforms as it hits the ground. Since the internal pressure increases because of the smaller volumne, the pressure increases accordingly, and temperature increases as well.. However, i don't know how to calculate the temperature with the given parameter..
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