Answer 1:
When it comes to gravity there are two key
issues we need to think about. First, the force of
gravity increases as the mass of an object
increases. The earth has roughly 80 times more
mass than the moon, so is the force of gravity 80
times stronger on earth? No, the force of gravity
is only about 6 times stronger on the earth than
on the surface of the moon. So why this
discrepancy? It relates to the second key issue:
size. The force of gravity decreases rapidly with
increased size (measured as distance to the
center). The earth is roughly 4 times as large as
the moon, meaning that we would expect the moon to
have roughly 4 times stronger gravity on its
surface than on the surface of the earth. When we
combine these two key factors - mass and size - it
ends up that the sheer mass of the earth gives it
a gravitation edge up and gravity ends up being
about 6 times stronger on the earth than on the
moon.
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