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  1. #1
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    Exclamation What is the minimum...

    what is the minimum energy needed to lift 1.0 kg to a height of 200 km and to give it a speed of 8.0 km/s?
    (neglect the small decrease of "g" over that distance)
    a) 34 KJ
    b) 34 TJ
    c) 34 MJ
    d) 34 J
    e) 34 GJ
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  2. #2
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    Quote Originally Posted by Celia
    what is the minimum energy needed to lift 1.0 kg to a height of 200 km and to give it a speed of 8.0 km/s?
    (neglect the small decrease of "g" over that distance)
    a) 34 KJ
    b) 34 TJ
    c) 34 MJ
    d) 34 J
    e) 34 GJ
    The minimum energy will be the amount of work to lift it 200 km = 2 x 10^5 m plus the amount of kinetic energy we are giving it. (v = 8.0 x 10^3 m/s). ALWAYS convert your units!

    So:
    mg \Delta h + (1/2)mv^2
     = (1.0)(9.8)(2 \, x \, 10^5) + (1/2)(1.0)(8.0 \, x \,10^3)^2
    = 33960000 J = 34 x 10^6 J = 34 MJ.

    -Dan
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