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Examples of conversion of gravitational PE to heat energy?

  1. Mar 31, 2017 #1
    1. The problem statement, all variables and given/known data
    I was looking for some examples where gravitational potential energy is converted to heat energy.

    Are there many such examples of this conversion? I could only come up with one such example and even that could be an incorrect example.

    2. Relevant equations
    PEg = mgh

    3. The attempt at a solution

    I tried to come up with an example but not sure of it's correctness. This example is as explained below.

    A meteorite falls towards earth due to earth's gravity and then disintegrates into pieces.
    As the meteorite travels in earth's atmosphere, the following changes in it's energy occur.
    • it's gravitational PE decreases due to decreasing height and this energy must get converted to other forms of energy
    • this gravitational PE gets partly converted to KE as the velocity of meteorite increases and partly to heat energy that results in temperature of the meteorite to rise(I am not sure if this is correct?)
    • when enough heat has been generated then the meteorite will burn in earth's atmosphere
    So, the following conversion occurs:
    PEg⇒ KEt + Q
    where PEg is gravitational potential energy (aka translational potential energy), KEt is translational KE and Q is heat energy
     
  2. jcsd
  3. Mar 31, 2017 #2
    In the real world for a falling body some the initial P.E is converted into heat due to air drag. Your example I think iscorrect but the heat created by the meteorite is not the main reason they burn up. For large meteorites it's due to the pressure they create.
     
  4. Mar 31, 2017 #3
    Here's an example: A bird taking care of business mid-flight and it lands on the roof of your car.
    Another example: You shoot your rifle vertically upward and, after you move out of the way, the bullet returns to earth and buries itself in the ground.
     
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