Freely Falling Bodies
In the 4
th
century BC, Aristotle thought that heavy objects fall faster than light
objects.
19 centuries later, Galileo argued that bodies should fall with downward
acceleration n that is constant and is independent of its weight.
Galileo was right,
the motion of falling has since been studied with great precision (when effects of the
air can be neglected).
In the absence of frictional drag, an object near the surface of the earth will fall with
the constant acceleration of gravity g. Position and speed at any time can be
calculated from the motion equations.
Illustrated here is the situation where an object is released from rest. It's position and
speed can be predicted for any time after that. Since all the quantities are directed
downward, that direction is chosen as the positive direction in this case.
Acceleration due to gravity
2
2
2
32
980
8
.
9
s
ft
s
cm
s
m
g
earth

=

=

=
2
6
.
1
s
m
g
moon

=
2
270
s
m
g
sun

=
Using the equations with constant acceleration, we have:
1.
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 Spring '11
 darp
 Acceleration, General Relativity, Light, Velocity, Galileo, Leaning Tower of Pisa

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