### A balloon on a bed of nails supports a surprising amount of weight!

Watch The Video:

Other Demos of Interest:

 Heating Water in a Balloon Imploding Soda Can Work Done by Expanding Air

Teachable Topics:

• pressure
• force
• surface area

Theory:

A balloon will pop when in contact with a nail because of the pressure exerted on the balloon by the nail.

Placing masses on top of the ballon increases the amount of force on the balloon.

A single nail provides only a small surface area to distribute the force over, which means all of the pressure on the balloon is concentrated on one nail. A small amount of force will thus provide enough pressure for the nail to pop the balloon.

Having the balloon rest atop many nails increases the amount of surface area that the balloon is in contact with. The pressure exerted on the balloon by each nail is thus less, enabling the balloon to withstand greater force before popping.

The same principles apply to large beds of nails that people lie on. The human body is able to withstand a certain threshold of pressure before feeling pain. Large beds with many nails are constructed such that the pressure is distributed over many nails (large surface area), so when lying on it you feel only a small amount of pressure from each nail, and not enough to cause pain. It's not magic, it's physics!

Apparatus:

• bed of nails
• balloons
• masses
• platform to hold masses in place

Procedure:

• to make a bed of nails:
• place nails through a board equidistant apart and at equal heights. Make sure they are no more than 1/2" apart.
• place balloon on top of bed of nails with platform resting on top
• gradually place masses atop the platform to see how much weight the ballon can withstand before popping!