Concepts

Moment of inertia, torque

Overview

Different objects can be rolled down a ramp to compare the rate of descent. Objects include a can of watery soup, a can of creamy soup, hoops, cylinders, and spheres. The watery soup should win a race with the creamy soup because the watery soup does not need to rotate and does not contribute much to the moment of inertia.

Details

Equipment

• [1] Wooden plank
• [1] Backstop with foam
• [1] Can of creamy soup
• [1] Can of watery soup
• [1] Wooden stick
• [1] Brass hoop
• [1] Aluminum hoop
• [1] Aluminum cylinder
• [1] Red billiard ball
• [1] Steel ball
• [1] Aluminum hoop with styrofoam filling and cylindrical steel core
• [1] Lab jack
• [2] C-clamp

Classroom Assembly

1. Set up an inclined plane with the plank and lab jack.
2. Place the backstop on the end of the ramp.
3. Attach C-clamps to the end of the table behind the backstop to prevent the backstop from moving very far after a collision.

Important Notes

• The differences in acceleration between the objects can be rather small, like for a sphere compared to a cylinder. To accentuate the differences, roll the objects along the full length of the ramp.
  
• Try not to let the cans and other objects acquire more dents!

Script

1. Ask students to make a prediction as to what objects will go faster moving down a ramp.
2. Place the two objects on the ramp, using the wooden stick to keep them from rolling down the ramp.
3. Raise the wooden stick to let them roll down simultaneously.
4. Repeat as necessary.

Additional Resources