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Trying to Understand Momentum

  1. Nov 6, 2007 #1
    hello everybody

    in a question in my text book i am asked to calculate my momentum when i am running at my estimated top speed, so i subbed in 10 m/s for the velocity and my weight is 80 kg and since the equation for momentum is P = mv i got the answer: 800 kg x m/s.

    Now i know that the definition of momentum is "the effect of an objects impact on another object is a function of the object's mass and its velocity" but i just cant understand what the definition for momentum has anything to do with me running, i guess i don't really understand completely what momentum is and i will really appreciate it if i can get any help with how momentum is there when a person is running, i just cant see it.

    thanks a lot!
  2. jcsd
  3. Nov 6, 2007 #2
  4. Nov 6, 2007 #3


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    Momentum is just a property that all bodies have (to be pedantic, an object does not need to have mass in order to have momentum).

    Think of it in a similar respect to inertia; imagine the sitution where someone is running at you, and you need to stop them. Now, the heavier the person is (the greater their mass is), the harder it will be to stop them, agreed? Likewise, the faster they're running at you, the harder it will be to stop them.

    So this property of theirs that resists a change in velocity (direction and speed), depends [directly] on their mass and velocity -- hence P=mv.

    Hopefully that helps a bit; but don't take this explanation too seriously. Momentum isn't a physical quantity which you can directly measure; just think of it as a useful mathematical quantity.
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