Video: Watch this demo
Description: This demonstration shows the force of atmospheric pressure.
Attach the hemispheres and use a vacuum pump to remove the air inside. Now have a student try and open it.
- Vacuum pump
- Magdeburg Hemispheres
- Plug the vacuum pump in and make sure it works.
- Have a small student pull apart the hemispheres with the vacuum pump off (easy).
- Now, turn on the vacuum pump and have a strong student try and pull them apart (very hard).
- Explain that since there is basically a vacuum inside the hemispheres, the atmospheric pressure is keeping them together.
- Explain that to open these, the student would have to pull with a force of about 250 pounds.
- (Optional) To do this out, say the radius of each disk is 1.6in. The surface area (pi*r*r) is thus about 16 square inches for both spheres. The atmosphere has on about 14.7 PSI, so that comes out to about 280 pounds of force.
- When finished, turn off the vacuum pump.