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Simple problem i need help with

  1. Sep 2, 2008 #1
    im new to the physics world and know this is probably an easy problem but i dont know where to start

    Hold a pencil in front of your eye at a position where its end just blocks out the moon. Make approprite measurements to estimate the diameter of the moon, given that the earth-moon distance is 3.8x10^5km.

    i figured that you prob had to measure the end of a pencil which i measured about 1.5 cm which is 1.5x10^-5km but i dont really know what to do from there.
  2. jcsd
  3. Sep 4, 2008 #2
    Your also need to also estimate the distance from your eye to the pencil.
    Draw a picture...there are two similar triangles involved
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