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Between the moon and the Earth a Spaceship travels

  1. Sep 25, 2005 #1
    between the moon and the Earth a Spaceship travels. A person goes on a spacewalk and pushes the tractor trailer sized vehicle. Will the person be pushed back even though things in zero gravity have no mass?
  2. jcsd
  3. Sep 25, 2005 #2
    There is still mass in space. You sure are pumping out a lot of questions Avgiu.
  4. Sep 25, 2005 #3
    Mass always has inertia, and an object's mass doesn't change either(only the weight changes).

    Similarly, if you were to try to kick a bowling ball in space, you would hurt your foot the same way as you would on earth.
  5. Sep 25, 2005 #4

    Doc Al

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    Staff: Mentor

    If the person pushes on the tractor, then the tractor will push back on the person. That's Newton's 3rd law.

    (1) Things still have mass regardless of gravity.
    (2) Not sure what you mean by "zero gravity"; gravity still exists between the Earth and the moon. (Unless you go to the exact spot where the attractions cancel.)
    (3) Perhaps you are thinking of weightlessness, which is not the absence of gravity, but the absence of a contact force supporting a body. It's only the apparent weight that is zero.
  6. Sep 25, 2005 #5
    If you pushed off of a tractor in space you would be pushed away from the tractor more than the tractor, You would experience most of the force of your push because the tractor has more mass, The more mass the tractor has the less force it will experience from your lesser mass and force of your push. Here's an analogy, Try jumping onto the earth and make it move, you do not have enough force to make a big difference, The Earth is a body in space just like the tractor.
    Last edited: Sep 25, 2005
  7. Sep 25, 2005 #6


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    Staff: Mentor

    No. The forces (due to Newton's third) are exactly equal. The accelerations are what are different.
  8. Sep 25, 2005 #7
    I used the word force in place of the word acceleration, Sorry. My bad. :smile:
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