Elusive Wealth

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Elusive Wealth Hold a peso bill so that the
midpoint hangs between a friends fingers.
Challenge your friend to catch it by snapping his
fingers shut when you release it. The bill wont
be caught!
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There was a young man who had heard, That a
person could fly like a bird. To prove it a
lie He jumped from the sky - His grave gives the
date it occurred!
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The Motion of Falling Objects
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Why do objects fall?
The force of gravity pulls down on all the
objects here on earth. Because of this force,
objects will tend to accelerate downwards
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At what rate do objects fall?
Regardless of mass, in the absence of air
resistance, all objects fall at the same rate.
Near the surface of the earth, this value is g
9.8 m/s2. This value is known as the acceleration
due to gravity.
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The Experiment at the Leaning Tower of Pisa
The Experiment at the Leaning Tower of Pisa
By dropping a heavy stone and a light stone
together, Galileo Galilei proved that they
accelerate and land at the same time.
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So, what explains this????
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AIR RESISTANCE!!!

• is the result of collisions of the object's
  leading surface with air molecules.
• determined by the objects speed and
  cross-sectional area

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AIR RESISTANCE!!!
Once the force of air resistance is as large as
the force of gravity, a balance of forces is
attained and the skydiver no longer accelerates.
The skydiver is said to have reached a terminal
velocity.
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When only the force of gravity is acting on a
falling object, the object is said to be in a
state of free fall.
When an object is in free fall, it changes its
velocity by 9.8 m/s (approximately 10 m/s) every
second.
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which explains why falling from the third floor
of a building hurts more than falling from the
remaining two or three steps down a flight of
stairs!
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EXPLANATION to ELUSIVE WEALTH   It takes at
least 1/7 second for the necessary impulses to
travel from the eye to the brain to the fingers.
But in only 1/8 of a second, the bill falls
approximately 8 cm (from y ½ gt2), which is
half the length of the bill.
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REACTION TIME You can compare your reaction time
with that of a friend by catching a ruler that is
dropped between your fingers. Let your friend
hold a ruler. Position your fingers at the 0 cm
mark of the ruler. Snap your fingers shut as soon
as you see the ruler released. The number of
centimeters that pass through your fingers
depends on your reaction time. You can find your
reaction time in seconds by solving y ½ gt2.
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Output Distance ruler has fallen in cm Trial
1_________ Trial 2_________ Trial
3_________ Average _______ Average in
m__________ Reaction Time (Show calculations
and correct units)
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Air Jordan
Basketball players, ballet dancers, and others
who have developed an unusual jumping ability
when leaping straight up seem to hang in the air
in defiance of gravity. We say they have a long
hang-time the amount of time airborne with
the feet off the ground. A common misconception
is that the greatest jumpers have hang-times of
more than 2 s. Surprisingly, the hang-time of the
greatest jumpers is almost always less than 1 s!
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HANG TIME Stand facing a wall, and with feet
flat on the floor and arms extended upward, make
a mark on the wall at the top of your reach. Then
make your jump and at the peak make another mark.
The distance between these two marks measures
your vertical leap. Use your ruler to measure
this distance in cm. Convert to m. Calculate your
time to reach the highest point. Double this time
to get your hang-time.
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Output Vertical leap in cm Trial
1_________ Trial 2_________ Trial
3_________ Average _______ Average in
m__________ Hang Time (Show calculations and
correct units)
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Sources www.physicsclassroom.com Conceptual
Physics, 8th ed. by Paul Hewitt Physics for You,
by Johnson www.mcwdn.org/SPACE/METEOR.GIFwww.aten
eo.edu