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Kinetic energy problem

  1. Apr 16, 2007 #1
    1. The problem statement, all variables and given/known data
    Is is possible to have a change in kinetic energy without providing an external force.

    2. Relevant equations

    3. The attempt at a solution

    I want some examples of the above mentioned problem. In radio active decay the alpha particles are coming out from the nucleus with a kinetic energy but we have not given any external force. is this example correct?
  2. jcsd
  3. Apr 16, 2007 #2


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    KE=(1/2)*m*v^2. The acceleration of a body without an external force is zero. Put the two together. In the example of radioactive decay the particle tunnels out of the nucleus. In this case are you correct is saying that the alpha particle had zero kinetic energy before doing this? (Consider the uncertainty principle).
  4. Apr 16, 2007 #3
    When a stationary thing explodes?
    Initially it does not have kinetic energy, but once its particles started moving in different directions..so net kinetic energy becomes more than 0.

    I think you just need to identify a source of potential energy in a system, it is exists then that energy can be converted to kinetic energy
  5. Apr 16, 2007 #4
    mass is a form of potential energy right?
    Last edited: Apr 16, 2007
  6. Apr 17, 2007 #5


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    Possibly. If you define 'external' other than as its definition in the second law.
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