› › › EXPERIMENTS
WHAT’S HAPPENING
The
variable-slope track helps you perform
experiments on the force of gravity. The track can
be set at different
slopes, or degrees of steepness.
At a less-steep setting, gumballs will roll
down the track slower than at a more-steep
setting. This is because the slope prevents the full
force of gravity from pulling the gumball down
the track. The steeper the track, the more gravity
can pull the gumball along the direction of the
track. The flatter the track, the more gravity will
try to pull the gumball into the track itself, where
it cannot go. This variable-slope track is a
simple
machine called an inclined plane.
At its lowest setting, gumballs actually get
caught in the track because gravity pulls them
away from the open end of the track.
Low slope
High slope
Experiment 3: Inclined plane
HERE’S HOW
1
Attach the
variable-slope track to the
tower. Connect it to the tower with a
straight pivot post and the variable-slope
track holder. Attach the hole of the track
holder to a peg on the same level as the
upper hole in the straight pivot post. This
results in a track with a high slope.
2
Roll a gumball down the track and catch it
at the end. Observe what happens.
3
Change the location of the track holder so
that its hole is on the same level as the
lower hole in the straight pivot post. This
changes the slope of the track.
4
Roll a gumball down the track again.
Observe what happens this time. Increase
the slope of the track until the gumball rolls
out of the track again.
Variable-
slope track
Straight
pivot post
Variable-
slope track
holder
Experiment 4: Friction
HERE’S HOW
1
Attach the
friction track to the tower at any
location.
2
Place a gumball at the top of the track. Have
your other hand ready to catch it at the end
of the track. Let it go. What do you observe?
Friction
track
WHAT’S HAPPENING
The
friction track has raised bumps on it. These
cause the gumball to slow down as it travels
down the track. They increase the friction
between the track and the gumball.
Friction is
the force resisting the motion of objects sliding
past each other. As the gumball rolls down the
track, it is releasing its potential energy as always.
It makes more noise than on a smooth track. The
increased friction is causing energy to be lost to
heat and sound. There is less energy to convert into
kinetic energy, so the gumball moves slower.
Gumball Machine Maker
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