Centripetal Force Marble

A marble is spun inside a glass. As the marble spins faster, centripetal force from the glass walls keeps it moving in a circular path, temporarily counteracting gravity.

1. Hold a wine glass (or any oval-shaped glass) upright by its base.
2. Drop a marble inside the glass.
3. Rotate the glass in a circular motion so the marble rolls around the inner surface.
4. Gradually tilt the glass sideways and then upside down while maintaining the marble’s circular motion.
5. (Optional) Place the marble in your palm and use the inverted spinning glass to scoop it up, getting it moving inside the glass.

Science minute: Exploring centripetal force - 9NEWS:

📄 Marble Gravitron - Steve Spangler: https://stevespangler.com/experiments/marble-gravitron-2/

• Try different glass shapes to see how the path of the marble changes.
• Spin marbles of different sizes or weights and compare how long they stay in motion.
• Use two marbles at once to observe their interaction while spinning.

• Adult supervision is required, especially when using fragile glass.
• Perform the demonstration over a soft surface like carpet to prevent breakage if the glass or marble is dropped.
• Keep marbles away from small children due to choking hazard.

• What force keeps the marble pressed against the inside of the glass? (Centripetal force from the glass walls.)
• Why doesn’t the marble fall when the glass is upside down? (The marble’s inertia and the centripetal force are stronger than gravity while spinning fast.)
• What happens when the glass slows down? (The marble loses centripetal force, gravity takes over, and it falls.)
• How is this similar to the amusement park Gravitron ride? (Both rely on circular motion and centripetal force to hold objects or people against the walls.)