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› › › EXPERIMENTS
Now that you have assembled the tower, let's
conduct a series of experiments to learn how
each track segment and stunt device works. All
of these parts attach to the pegs on the sides of
the tower, and each one can be used to
demonstrate physics principles.
Experiment 1: Force and Motion
HERE'S HOW
Attach the 180-degree smooth track to the
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tower at any height. Two of the holes attach
to pegs on the same level, and the third
attaches to a peg one level down. You have
to stretch the track a little to get it to fit onto
the pegs.
Position a gumball at the top of the track.
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Have your hand ready to catch it at the end
of the track. Let it go. What do you observe?
WHAT'S HAPPENING
The 180-degree smooth track is the simplest
track segment. A gumball rolls from the top to
the bottom, 180 degrees around the tower. This
simple motion demonstrates many things. The
gumball has mass. Mass is the quantity of
matter in an object or a body, which is a physics
term for a physical thing. Matter is any physical
substance that occupies space. Mass can also be
thought of as the ability of a body to be heavy.
Mass should not be confused with weight
though. Weight is a measure of the force that
gravity exerts on mass.
A force is the cause of a change in a body's
state of movement. A force can be thought of as a
push or a pull on an object. A push of the gumball
causing it to roll across the table is a force.
Gravity is also a force. It is Earth's force of
attraction on mass. Gravity is a fascinating
thing: All mass attracts each other. The larger
the mass, the greater its force of attraction.
Earth has a huge mass: 5.9 trillion trillion
kilograms, or 13 billion trillion tons! The
gumball has a very small mass: about two
grams. Therefore, Earth pulls the gumball
toward it. This is the force of gravity!
A gumball rolls down the track because
180-Degree
smooth track
gravity is pulling it. On Earth, the gravity at the
surface is a downward force that causes an
acceleration equal to about 9.8 meters per
second per second (m/s/s or m/s
To understand acceleration, we have to
understand speed. Speed is the distance traveled
by a body in a certain amount of time. Velocity is
a physics term for speed that also takes into
account the direction of motion.
If a gumball travels five inches in one
second, its speed is five inches per second, or 5
in/s — which is equal to about a quarter of a
mile per hour.
Acceleration is the measure of the change in
speed (or more accurately, velocity) over a
certain amount of time. So, what is gravity
again? Earth's gravity causes a body to
accelerate to a speed of 9.8 meters per second
for every second that gravity acts on the body —
regardless of the mass of the body. If you drop a
gumball and it falls for three seconds, by the end
of its fall, it is moving at a speed of 29.4 meters
per second (9.8 m/s
2
x 3 s = 29.4 m/s).
As the gumball rolls down the track, gravity
accelerates it and it moves faster, unless it
encounters obstacles.
Amazing! This one simple segment of track
has allowed us to define all these physics terms.
Gumball Machine Maker
).
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