Blow up a long cylindrical balloon and it inflates according to Laplace's law. Arteries, which also need to be flexible, are designed to fight against the kind of aneurysms seen in inflating rubber balloons.
When two different size soap bubbles are connected together, the smaller diameter bubble will shrink and collapse to blow up the larger diameter bubble. One can use this to demonstrate Laplace's law or the phenomenon of minimizing the surface area of a soap film.
How it works
Laplace's law tells us that the gauge pressure of a spherical membrane is given by 2γ/r, where γ is the surface tension and r is the radius of the sphere.1 For soap bubbles (which have an inside as well as outside surface), the gauge pressure is twice...
The concept of pressure is demonstrated by lying on a bed of nails.
What it shows:
The lecturer (or someone else) lies on a bed-of-nails without discomfort, thus demonstrating the concept of pressure, which is the force per unit area. For added drama the person is sandwiched between two beds of nails with the added weight of a cinder block on top. The cinder block can be broken with a sledge hammer.
figure 1: A supermarket tabloid reports on how macho man pulls off this stunt. ...