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WHAT’S HAPPENING
The
domino track offers another lesson in transfer
of momentum. When you knock over the domino
with your finger, it causes the other dominos to
fall, but it probably doesn’t push the gumball off
the post. Then, when you drop a gumball into the
top of the domino track, it knocks down the
dominos, and the last domino pushes the
gumball off the post.
In both cases, when the first domino falls over,
a chain of collisions follows, in which each domino
knocks down the next. The final domino falls over
and collides with the gumball positioned on the
post. Whether or not the final domino pushes the
gumball off the post is determined by the
momentum of the domino. The momentum from
your finger push or the first gumball falling into
the track is transferred through the dominos. Thus,
you can conclude that the falling gumball has
more momentum than your gentle finger tap.
Experiment 5: Centripetal force
HERE’S HOW
1
Attach the
centripetal force funnel to the
tower at any location.
2
Toss a gumball into the funnel. Have your
hand ready to catch it beneath the funnel
spout. What do you observe?
Experiment 6: Collisions
HERE’S HOW
1
Attach the
domino track to the tower at any
location. Insert the six
dominos by carefully
clicking them into the slots. Insert the small
domino track post at the end of the track. Flip
all the dominos so they are standing upright.
2
Balance a gumball on the domino track post.
Have your hand ready to catch it when it falls.
Gently tap the uppermost domino over with
your finger. What do you observe?
3
Reset the dominos into their upright positions.
If the gumball fell off the post, reposition it.
Now try dropping a gumball into the top of
the domino track. What happens now?
Domino track
with post
6 Dominos
Centripetal
force funnel
WHAT’S HAPPENING
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.
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