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Math Help - gravity and energy problems

  1. #1
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    gravity and energy problems

    A 920kg satellite is projected vertically upward from Earth's surface with an initital kinetic energy of 7.0x10^9J. Find
    a)its max height
    b)the initital kinetic energy it would have needed to keep going indefinitely
    c)the inital speed it would have needed to keep going indefinitely.

    which equations would I use for each part?
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  2. #2
    Senior Member topher0805's Avatar
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    I'm not very good at helping people with math, but I'll give it a shot.

    Perhaps you can use the physics formula, v=\sqrt{\frac{2K}m} to figure out initial velocity.

    The acceleration due to gravity is 9.8m/s^2. However, you can not simply use d=vt + \frac{1}2at^2 to figure out the max height because as you get farther from earth, gravity decreases.

    What you need to do is use the gravitational constant, G. It is approximately equal to 6.67 x 10^-11.

    Hmm, this is harder than I thought. I'll have to think about it for a while.
    Last edited by topher0805; February 6th 2008 at 10:13 PM.
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  3. #3
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    I wasn't able to get the correct answers from using the above formulas. Are there different equations I can use?
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