Pressure (Nadia Chocron)
Author
Nadia Chocron
Principle(s) Illustrated
Pressure is force over area.
The more area there is, the less pressure there is.
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.