› › › PHYSICS EXPLANATIONS
Low slope
High slope
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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. You
connect it to the tower with a straight pivot post and
the variable-slope track holder. The holder can be
attached to the tower with its arm up or down,
allowing you to position the variable-slope track at
two different angles.
At its less-steep setting, gumballs will roll down
it slower than at its 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.
Every track and stunt also enables us to investigate
work and energy.
Work is force exerted over a
distance. When you move a gumball from the bottom
of the tower up to the top with your hand, you
perform work. Moving a body requires work.
Energy
is the capacity of a body to do work.
Energy is required to move a body over a distance.
Energy comes in many different forms, and it can be
converted from one form to another. This gumball
machine demonstrates two types of energy: potential
energy and kinetic energy.
Potential energy is stored energy. Kinetic energy
is the energy of motion. The gumballs at the top of
the machine have potential energy. When a gumball
starts rolling down the track, its potential energy is
converted into kinetic energy. At the bottom of the
track, it has less potential energy than at the top. You
must put energy back into it with your hand by
raising it back up to the top.
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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.
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The
centripetal force funnel demonstrates
rotational inertia, or moment of inertia, and
centripetal force. When a gumball enters the funnel,
the shape of the funnel causes the gumball to curve
around in a circular motion. As the gumball slows
down, it circles closer and closer to the center, and
then falls into the hole.
Centripetal force is the reason the gumball
doesn’t just roll straight into the hole. Centripetal
force is a force that makes a body follow a curved
path. Like inertia, the
rotational inertia of the
gumball describes its tendency to remain in motion
and resist slowing down. But because friction and
gravity work to overcome its inertia, the gumball
slowly gets closer to the hole in the center.
Gumball Machine Maker
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