1 small table or other long, flat area that kids can stand on
Inflate the balloons about half way, tie them off, and place them on the floor.
Turn the small table over and place it on the balloons.
Holding the table stady help your children stand in the center of the table.
Ds#1 knew right away that the balloons would not pop, though he thought it had more to do with the balloons not being directly under his weight.
They noticed how the balloons changed shape; I pointed out that all 4 balloons changed because the weight (force) in the center of the table created pressure in all 4 balloons and was, in fact, divided among the balloons. Also, the balloons spread out so that more area touched the table, which decreased the pressure on any one spot.
When you do it, put the balloons under the table a bit more, otherwise the corners of the table can dig into a balloon if a child does not step directly onto the center of the table. Ds#3 stepped up with ds#1 for a total combined weight of about 100 lbs. Ds#2 had a fever and only wanted to look on.
The standard unit of Pressure is 1 pascal (Pa) = 1 Newton/m² = kg/(m· s² ), named after Blaise Pascal, who invented the hydraulic press and the syringe, among other things. The Imperial equivalent is psi, or pounds per square inch.
You can also demonstrate this using straight pins. Tape graph paper to cardboard. Stick a pin through every corner. Place an inflated balloon on the pins and a brick on top of that. Just like the bed-of-nails trick!
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