Kinetic & Potential Energy

4) Students will be asked to describe when they believed that the rollercoaster had the most energy.

5) Students will refer to the website:

http://www.gmhsscience.com/problems/kineticpotential.htm

for the following information and lab activity.

Kinetic and Potential Energy

Energy is defined as the ability to do work. When the work is actually being done, we term the energy "kinetic." When the work is waiting to be done, when there is the potential for work to be performed, we term the energy "potential." Kinetic energy is the energy of motion, potential energy comes from work having been done on an object which was then stored. For example, a rubber band zinged from your finger has kinetic energy. While it was stretched, waiting for you to release it, it had potential energy. The rubber band was stationary, but work had been done on it to move it to its present position.

Now, we know that the further we pull back a rubber band, the faster and further it will fly. Consider this situation in terms of potential and kinetic energy. When I pull back the rubber band to a great distance, I am doing more work to it than if I pulled it back only a small distance. More work means more energy is provided to and stored by the rubber band. When I release the rubber band, it has more energy to move. More energy means more work can be done by the rubber band. There is a connectedness, then, between potential and kinetic energy for matter.

6) Students will write notes based upon the information found on the website in an Appleworks file.

Conclusion and Evaluation: Students will create their own rollercoasters as described in the following websites.

http://www.kidsoutandabout.com/science/looptheloop.html

Loop-the-Loop

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.