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Are astronauts weightless in orbit?

  1. Jul 31, 2010 #1
    1. The problem statement, all variables and given/known data
    If someone told you that astronauts are weightless in orbit because they are beyond the pull of gravity, would you accept this statement? Explain.


    2. Relevant equations



    3. The attempt at a solution
    I say no. There is still gravity, but its just weaker with distance.

    Can someone help me understand the concept? Am i in the right direction?
     
  2. jcsd
  3. Jul 31, 2010 #2

    PhanthomJay

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    Correct.
    Gravity is a bit weaker, but only about 10% weaker. That does not explain their apparent weightlessness.
    You are not in the right direction. What causes their apparent weightlessness? A 200 pound astronaut still weighs about 180 pounds a few hundred miles up.
     
  4. Jul 31, 2010 #3
    Think bigger...
     
  5. Jul 31, 2010 #4
    They are weightless because they are in free fall. The only force acting on them is gravity. In this case, Earth's gravity.
     
  6. Jul 31, 2010 #5
    True, but what makes weight is gravity and an opposing force. So weightlessness and gravity doesn't go together. They are simply masses with no external forces apart from the gravity ...thus, in free fall.
     
  7. Jul 31, 2010 #6
    so would that be the answer, because they are in free fall?
     
  8. Aug 1, 2010 #7

    PhanthomJay

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    Yes, when an object or person is subject to gravity forces only (no contact forces),it is said to be in a state of 'free fall' . It's like dropping an object from a tall building (assuming no air resistance); the object still has weight (W=mg) during its decent, but because there is no contact force acting on it, it is 'apparently' weightless during the fall ( a scale attached to the botton of it would read zero). Of course, an astronaut and his/her ship does not fall straight down to earth in exactly the same way, becuse of its high speed keeping it in orbit due to the centripetal force supplied by earth's gravity causing it to move in a circle while nonetheless continuously 'falling' toward earth.
     
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