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According to
Newton's law of universal gravitation,
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the earth's
gravity gets weaker as we go further
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from the earth.
But when we drop a ball
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near the top of
the lecture hall it doesn't
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seem to fall any
differently than we drop it
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near the floor.
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Let g t stand
for the gravitational acceleration
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observed at the
top of the lecture hall and g b for it
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at the bottom.
Estimate how much
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Newton's
universal gravitation theory predicts g t
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will be less than
g b .
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(Hint: It's
easier if you estimate
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the fractional
change, g b /g t - 1.)
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