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Need some quick physics 110 help

  1. Jul 12, 2011 #1
    this should be obvious, but I'm a little confused. Question is, ' If an object weight 100 pounds on the earths surface (4k miles from the center), is moved to 4000 miles above the surface. How much does it weigh?'

    f=Gm1m2/r2, so you would square the r, which means you would divide Gm1m2 by 4 correct? So 25 pounds?

    2.) An object on the surface of earth that weighs 100 pounds is moved to a planet with 5x the radius and that is 2x as large, how much does the object weigh?

    so it would be Gm1m2/r2= 100 lbs.

    G(2)m1m2/52= 2/25 = 1/12.5.-- 100 * 1/12.5 = 8 lbs.

  2. jcsd
  3. Jul 12, 2011 #2
    It looks all right.
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