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Homework Help: Newton's Laws to explain !

  1. Oct 23, 2014 #1
    Use Newton's to explain :

    When you take a step, you push down and back on the earth and the earth pushes up and forward on you. When you step on a skateboeard, the skateboard moves backward as you push down and back. Why does the skateboard move backward while the earth does not even if the force is the same?
  2. jcsd
  3. Oct 23, 2014 #2


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    Gold Member

    What makes you think the Earth doesn't move?

    How much more massive is the Earth than a skateboard?
  4. Oct 23, 2014 #3
    Could you explain why ? I need details for this answer
  5. Oct 23, 2014 #4


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    Gold Member

    Sorry. I went back and edited my answer once I realized that this is a homework question.

    If you are studying Newton, you are familiar with F=ma?
  6. Oct 23, 2014 #5
    I need to explain details for this question
  7. Oct 23, 2014 #6

    Simon Bridge

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    Homework Helper

    It would defeat the point of the exercise if any of us provided you with a detailed answer.
    You have to provide the details yourself.

    But the start has been given to you. The questions are there to guide you.
    If you try to walk on a wheeled platform, i.e. the skateboard, the platform goes backwards over the ground ... why does it do that? Can you tell us in your own words?

    If you walk on the Earth ... you have to push on the Earth. The Earth is just another mass ... what happens to masses when you push on them?
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