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Thread: Question about gravitational constant

  1. #1 Question about gravitational constant 
    New Member
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    Hi all, my first post (if you don't count my intro)

    Suppose we have two rockets in space. They are not moving relative to each other. Rocket 1 fires x amount of thrust causing it to reach speed y relative to Rocket 2.

    Now humor me for a moment: if the gravitational constant was twice as strong, it will still take the same amount of thrust to reach speed y, not twice the thrust, correct? Am I right in that the gravitational constant has no effect on the amount of thrust to reach a given speed?

    Thus if G was twice as strong, a 1 kg object would still use the same thrust to move, but its gravity would be as if it were 2 kg.


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  3. #2 Re: Question about gravitational constant 
    . DrRocket's Avatar
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    Quote Originally Posted by Superluminati
    Hi all, my first post (if you don't count my intro)

    Suppose we have two rockets in space. They are not moving relative to each other. Rocket 1 fires x amount of thrust causing it to reach speed y relative to Rocket 2.

    Now humor me for a moment: if the gravitational constant was twice as strong, it will still take the same amount of thrust to reach speed y, not twice the thrust, correct? Am I right in that the gravitational constant has no effect on the amount of thrust to reach a given speed?

    Thus if G was twice as strong, a 1 kg object would still use the same thrust to move, but its gravity would be as if it were 2 kg.
    If you can ignore the gravitational attraction of the second rocket and if "in space" means that the gravitational fields of stars, planets, etcc. can be ignored the the gravitational constant is irrelevant.

    The speed of a rocket subject to no external forces relative to inertial reference frame with respect to which it is initially at rest is



    where is the speeed of the exhaust gasses relative to the rocket.

    Note the absence of the gravitational constant in the above expression.


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  4. #3  
    Forum Radioactive Isotope MagiMaster's Avatar
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    Also, don't confuse mass and weight. A 1 kg object would still be 1 kg (a gram being a unit of mass, not weight).
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