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Inertia and a Rocket that doesn't accelerate anymore

  1. Feb 22, 2015 #1
    Let's say we are on Earth-like planet, but without an athmosphere.
    There's a rocket on the ground and it's starting now. The rocket accelerates but at a point when it has enough speed it stops accelerating. The rocket has still enough speed to get further away from the planet but not enough to escape the planets gravity field.

    So the rocket has stopped to accelerate but still has enough speed to get further away from the planet, does an astronaut now feel any kind of inertia? Is he floating in the rocket?
  2. jcsd
  3. Feb 22, 2015 #2


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    The rocket blast accelerates the rocket. It is the rocket pushing on the "astronaut" that she feels as pressure. When the rocket stops, she no longer feels that and will be in "free fall".
  4. Feb 22, 2015 #3
    What do you exactly mean with "stops"? When the acceleration stops or when the rocket reaches the point when it falls down back on the planet.
  5. Feb 22, 2015 #4


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    By "the rocket stops" I meant when the rocket engine stops so there is no more acceleration. I should have said "engine". Thanks for asking so I could clarify that.
  6. Feb 22, 2015 #5


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    Staff: Mentor

    That does not matter, by the way.

    An astronaut will always feel inertia (it takes some effort to accelerate inside the rocket), but if we have no atmosphere and the rocket is not using thrusters*, the astronaut will always float inside the rocket.

    *and assuming the rocket does not have ground contact, of course
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