### Rockin' Roller Coaster

Before introducing physics students to the Law of Conservation of Energy and the Principle of Conservation of Mechanical Energy, I let them spend a class period building "roller coasters" using common materials It gives them the chance to discover these concepts that are such an integral part of the amusement park experience. This activity emphasizes discovering the physics behind roller coasters through hands-on experimentation.

Form for submitting answers to questions for this activity.

Objectives:

• Students will relate gravitational potential energy to mass and height.
• Students will relate kinetic energy to mass and speed.
• Students will demonstrate the relationship between potential and kinetic energy.

Materials:

• 16 foot long piece of pipe insulation, cut in half, for each student group
• duct tape
• cardboard to support their designs in place
• marble
• scissors (for cutting tape and cardboard)
• meter stick
• stopwatch

Requirements:

1. Students will not cut their pipe insulation.
2. Students will create a working roller coaster from the materials provided.
3. The roller coaster shall have at least one steep hill and one low hill. It should also contain at least a single loop-the-loop.

Evaluation:

After a day of building and testing, follow-up discussion emphasizes the concepts of physics represented in the project.

1. Problem: Predict loss of energy.
Activity: Build a large hill/small hill combination such that the marble just crosses over the small hill.
• Observations:
1. What happened to the speed of the marble as the height changed?
2. Where was the speed the highest? The lowest?
3. What is the ratio of the height of the large hill to the height of the small hill?
• Conclusions:
1. Why isn't the ratio of the height of the large hill to that of the small hill 1:1?
2. Relate this ratio to the potential energies of the large hill and of the small hill. What happened to your loss of potential energy? (answer in terms of work)
3. Predict what would happen if the initial height was increased and the small hill height stayed the same. Why does this happen?
4. Predict what would happen if the second hill was higher than the first. Why does this happen?
2. Problem: Predict where a marble must start to successfully negotiate a loop-the-loop of maximum diameter.
Activity: Build a loop-the-loop whose diameter is as large as possible such that the marble just clears the top of the loop.
• Observations:
1. What is the ratio of the height of the hill to the diameter of the loop?
2. Where was the speed of the marble the greatest? The smallest?
• Conclusions:
1. How does your ratio compare to the ratio of the heights found in problem one? Why do you think they are similar?
3. Summing up:
• Describe in your own words the energy changes that began with lifting the marble to the top of the large hill through traversing the entire roller coaster.
• Describe in your own words when work was done and what is was done against.

Lesson based upon an article titled Students Take Concepts from AstroWorld Rides to Build Roller Coasters, Houston Chronicle, section A, page 22, Monday, June 6, 1999. Permission to use roller coaster pictures granted by Jason Knutson.