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Experiment 11: Pulleys
HERE'S HOW
Attach the pulley wheel to the tower at a
1
relatively high location using the straight
pivot post. Tie one end of the string to the
arm of one pulley cup. Tie the other end of
the string to the arm of the second cup. Hang
the string from the pulley wheel with a cup
on either side.
Drop a gumball into one of the cups. Drop a
2
gumball into the other cup. What happens?
WHAT'S HAPPENING
The pulley cups and wheel demonstrate a simple
machine called a pulley. This setup shows how a
downward force (the weight of a gumball) applied
to one side is transformed into an upward force of
Experiment 12: Center of mass
HERE'S HOW
Attach the tip-over tube to the tower at any
1
location using the angled pivot post. If the
tube slides down in the clamp, stretch a
rubber band in an X shape over the ends of
the clamp to hold it in place. The tip-over
tube should be positioned high up in the
clamp. More of the tube should be above the
clamp than below the clamp.
Drop gumballs into the tube one at a time.
2
After each drop, try to tip the tube over. As
the tube fills up, what do you notice?
WHAT'S HAPPENING
Like the pendulum, the tip-over tube demonstrates
center of mass and stable equilibrium. When
gumballs fall into the tube, they will stay in the
tube until the center of mass extends outside of
the stable equilibrium point and the tube tips
over, dumping the gumballs into the track below.
Now that you know how all the tracks and stunts work, follow the step-by-step assembly instructions on
the following pages to set up three expert-level gumball machines that use many of the parts together.
Gumball Machine Maker
Pulley
wheel
String
Pulley
Straight
cups
pivot post
the cup on the other side. Pulleys can change the
direction of a force, and also the amount of force
needed, to perform work. If you place two gumballs
in the second pulley cup, you probably will need
two or more gumballs to fall in the first pulley cup
before it exerts enough weight to lift up the second.
Angled pivot
post
Clamp
Tube
Rubber band
crossed
in X shape
Tips for the tip-over tube:
If the tip-over tube doesn't tip over, try moving
the angled pivot post down one peg on the
tower, and positioning the tube higher up in the
clamp. Also, experiment with starting with
different numbers of gumballs in the tube.
Move pivot
post down
and tube up
11
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