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Science Experiment from the RMSC
Loop-the-Loop

RMSC

Materials Needed:
Flexible tubing
Marbles
Chairs and/or tables

What to do:

Take your tubing and make a rollercoaster out of it! Bend it and twist it. Make big loops or little loops! Try anything you want!

You need to secure the tubing to chairs or tables so that your rollercoaster won't fall down. What would you like to use to secure your coaster? Do you think tape is strong enough? What about twist ties from garbage bags, or maybe pipe cleaners?

You also need something to catch the marble when it gets to the end of the rollercoaster. What would you like to use? See what works best, but be careful not to use anything that might break, like glass.

The Experiment:

Once your rollercoaster is ready, put a marble at the top and let the ride begin!

Do you think the marble will make it all the way?

Where do you think it might get stuck?

What can you fix so that it won't be stuck anymore?

Do you think it matters how high it starts?

How big can you make a loop and not get the marble stuck?

Why?

There is a very important law in science called Conservation of Energy: Energy cannot be created or destroyed, but can change form.

When your marble is at the top of the hill on the rollercoaster, before it starts rolling, it has potential energy. When it is moving, it has kinetic energy.

Conservation of Energy means that the amounts of kinetic and potential energy must be the same.

As it rolls down the hill, the marble goes faster, and more and more potential energy is converted to kinetic energy. When the marble rolls back up a hill, the opposite happens. The marble slows down, and kinetic energy is converted back to potential. If you don't start the marble high enough, it may not have enough kinetic energy to get up to the top of the next hill.

Now, think about a ball on a string.

If you swing the ball in a circle, it keeps moving and it feels like the ball is pulling your arm to the outside.

Actually, there is a force that is directed from the ball toward your hand that keeps the ball from falling when it goes up. This is the same force that holds the marble on the track when it is upside down.

A force is a push or a pull. There is another important law called the Third Law of Motion: For every force there is an equal and opposite force. So the force you feel is the force that is opposite of the one holding the ball in place! The circular motion causes the ball to "feel" a force toward the center of the circle: your hand. This force is the same force that keeps the car on the rollercoaster when it is upside down in the loop. As long as this force is greater than the force of gravity (the force that pulls us toward the earth), the car doesn't fall when it reaches the top of the loop.