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Universal Gravitation- please help!

  1. Nov 21, 2005 #1
    The center-to-center distance between Earth and Moon is 384400 km. The Moon completes an orbit in 27.3 days.
    (b) If gravity were switched off, the Moon would move along a straight line tangent to its orbit, as described by Newton's first law. In its actual orbit in 1.00 s, how far does the Moon fall below the tangent line and toward the Earth?

    part (a) was asking for the Moon's orbital speed which was 1024 m/s. for part (b) my question is I don't know what equation to use to solve for this. All i know is that I need to use centripetal acceleration but when?
    thanks and i hope you can help~!!
  2. jcsd
  3. Nov 21, 2005 #2


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    The second part is a geometry problem.
    Consider a circle with a tagent line drawn at one point. Now after 1.0 s, the moon (under gravity) moves through an angle of theta. I truly think this needs a diagram, so I've attached one now. We want to solve for y.

    Last edited: Nov 21, 2005
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