Go here to see the Two Minute Science: Centrifugal Force Video.
DIRECTIONS to make swinging platform
Wood or plastic platform, about 30cmx30cm
Plastic cups to hold water
Optional: nonslip drawer liner
Drill and ¼” drill bit
Optional: Hot glue gun with hot glue sticks
Drill a hole in each corner of the platform, about a centimeter inward from the edges.
Thread a long string of twine through the holes in a way that the twine crisscrosses to support the platform underneath it. Make the twine long enough so that you can hold the twine and suspend the platform in the air.
Optional: Hot glue a piece of nonslip drawer liner to the platform.
SWING your cups round and round!
Fill the cups with water to about the halfway mark. If you are not confident about swinging platform with cups of water, you can put rubber balls in the cups and do a few practice rounds!
Don’t hesitate into your swing, and do a few in a row! When you are ready to stop the platform, slowly let it swing like a pendulum until it slows down and you can gently come to a stop.
CENTRIFUGAL force, explained
The platform’s speed and direction are constantly changing as it swings in a vertical circle. The force of gravity speeds the platform up on the way down and slows the platform down on the way up. The tension in the twine keeps the platform from flying off tangent to its circular path. The combined forces of gravity and tension are what we call centripetal force, and what the platform and cups experience is called centrifugal force. Likewise, when you go around a rollercoaster loop, the force of gravity combines with the normal force of the rollercoaster track to keep you in your seat, and that feeling of being pushed into your seat or the sides of the compartment is called centrifugal force.