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Moving oneself when in freefall?

  1. Feb 22, 2007 #1
    Here is an extract from a textbook.

    "While jumping or diving or on a trampoline a person will experience apparent weightlessness for a very short time. They will be in 'free fall'. It is much easier in these conditions to move your arms and legs since the force of gravity does not need to be overcome. Standing still and holding your arms out horizontally can be very tiring but a diver or gymnast in motion can move their limbs easily."

    Is this correct? Moving ones arms out horizontally when in free fall while trampolining is just as difficult as when standing on the ground because the graviational force on your arms is constant when in free fall or not near the earth.
  2. jcsd
  3. Feb 22, 2007 #2


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    Yes, it's right. When in free-fall, your muscles are not exerting to keep your arms up against their weight; they are allowed to fall.
  4. Feb 22, 2007 #3
    But you are purposely extending your arms out from a relxed, dangled position. It's like trying to lift a weight a height d while in free fall relative to you. You still have to do work=Fd in lifting this weight. However, I agree you will not feel your own weight because there is no normal force in this situation. However, when lifting (relative to you) whether a weight or your arms, you create the normal force.

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