Dramatically show that pressure is a force per unit area with this familiar demonstration. Place an inflated balloon on a wood block full of sharp nails. Add a 1000-g mass to the “floating” board on top of the balloon and amazingly the balloon does not pop! Continue adding more weight until the balloon pops. Repeat the demonstration using a single nail. Which bed of nails will support more weight before the balloon pops? The wood block with many nails holds significantly more weight without popping the balloon compared to the single-nail block. This effectively shows that as the surface area (number of nails) decreases, the pressure increases. Multi-holed board allows for a variety of nail quantities and combinations to show increasing or decreasing surface area.
Concepts: Pressure, force, surface area. Time Required: 15 minutes Materials Provided: Bed of nails, 50 balloons. Note: Replacement balloon are available. A weight set is required and available separately.