Extreme Science: Penny Shine

What you will need:

  • Quarter
  • Crisp one dollar bill
  • Patience……
  • Adult supervision


1. Fold your dollar bill in half lengthwise as shown:

2. Try balancing your quarter on top of the dollar bill as shown:

3. Now, try folding your dollar bill in half so that it makes an “L” shaped “tent” as shown:

4. This time, place your quarter on top of the dollar bill so that the center of your quarter is balanced over the top of the vertical fold in your dollar bill as shown. Now, SLOWLY straighten out the dollar bill so that it stands straight as in step one. The quarter should slowly adjust itself to a balanced position. This does take practice.

What is going on?

As you have probably noticed by now, it is very difficult to balance a quarter on the edge of the dollar bill. Although it is possible, it takes time and patience to accomplish this. In order to balance an object, we must find its center of gravity. This is the point where there is an equal amount of weight on either side of the balance point. When you fold the dollar bill to create an “L” shape and centering the quarter over the fold, you are allowing gravity to help you find the balance point, or center of gravity, of the quarter. As you slowly straighten out the folded dollar bill, the quarter will gradually shift from side to side due to friction and gravity. When the quarter is not centered over the edge of the dollar bill, this will cause greater pressure on one side of the quarter to the dollar bill. As the dollar bill continues to straighten out, the quarter will automatically adjust as its mass, or weight increases or decreases on each edge of the dollar bill. If you can straighten the dollar bill out in a smooth motion, you will find that once the dollar bill is completely straight, the quarter has now perfectly balanced itself on the edge of the dollar bill.

Try this:

Do you think that it would be easier with a larger coin such as a fifty cent piece or silver dollar or a smaller and lighter coin such as a dime? Try it and see!

Radical Rick

Extreme Science



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