For Educators

Bottle "Tops"
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Learn About

physics | rotation | wobble

Materials Needed

Crown cap, like from a glass soda bottle, like IBC root beer; thin nail; hammer; permanent markers of different colors


1. Place the crown cap, bottom side up, on a piece of wood.

2. Take the thin nail and place the point in the center of the cap. Tap the nail with a hammer so that an indentation is made in the cap. DO NOT hammer the nail all the way through the cap.

3. Placing the nail into the indentation, give the nail a quick twist with your fingers to spin the cap. What happens? Does the cap wobble? What makes the cap wobble? Try to see whose cap can spin the longest, or with the least spin.


Now, explore! Use markers to draw designs in the cap. What happens to those designs or the colors when you spin the cap?

What's Going On

When you give the nail a twist, you give the cap a spin, just like a top. The indentation provides an axis of rotation. The wobble is due to placing the hole off center. This puts more weight to one side of the axis of rotation than on the other making the top no longer balanced. Maybe you notice that the more unbalanced the cap, the shorter the "spin time". This is due to the wasting of energy on the wobble that could have been used to make the top spin longer.

Ohio Content Standards

Physical Science: 9.20
OSIC Codes: Y2002.CSC.S03.G09-12.BG.L09.I20
  • Added: November 29, 2011
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