Projects‎ > ‎(1) Discrepant Events‎ > ‎

## Principle(s) Illustrated

1. Pressure is force over area.
2. The more area there is, the less pressure there is.
3. Pressure and area are inversely proportional.

## Standards

• 8. a. Students know a force has both direction and magnitude.

• 8. d. Students know how to identify separately the two or more forces that are acting ona single static object, including gravity, elastic forces due to tension or com­ pression in matter, and friction.

## Questioning Script

Prior knowledge & experience:

Students already know that the nails on the bed of nails are sharp and will pop the balloon.  The students know that balloons can pop.

Root question:

Why is the bed with more nails able to have more force without the balloon popping?  Why does the single nail pop with less force?

Target response:

The bed of nails is spread over a bigger area, so the pressure is less and the balloon is not popped.  THe single nail has less area, so the pressure is greater, popping the balloon easier.

Common Misconceptions:

Students believe that is one nail pops the balloon with little force, the bed of nails should pop the balloon immediately.

## Photographs and Movies

The bed of nails comes with a single nail and a bed of nails.  The balloon is placed on the nails or nails and weights are added to the top.

## References

Pressure Demonstrations

Pressure Demonstrations