Gravity Well

This demonstration is used to visually display the orbital motion of a planet around a star in its gravitational field. A ball orbits in the well, picking up speed as it gets closer to the center. This helps students visualize Kepler's Second Law.

* Equipment seen in the leftmost video may vary from equipment used in ND Demonstrations. See information and images below for ND equipment and setup.

New Set-up available upon request (below), but need at least three days for set-up and organization

Setup:

Connect the PVC pipes together into an octagon. Place sheet across pipes and use clamps to hold it in place. Hang hangers and masses from paperclips attached to center of well. Place the ball in the well, give it an initial tangential velocity and release to see orbits. The ball will orbit and eventually speed up and fall into the center of the well.

Notes:

This demonstration may require a little practice to get the desired orbits.

Courses Used In:

• PHY 10111

• PHY 10310

• PHY 10410

• PHY 30210

Discussion and Polling Questions:

• If we replaced a large ball with a small one with the same mass, would the orbits change? (Relate to replacing the sun with a solar-mass black hole)

• How would the orbit change if you had two equal masses instead of a big and small mass?

Equipment Needed:

• PVC pipes with connectors

• Sheet

• Clamps to hold sheet

• paper clips

• hangers with masses

• Assorted Balls