Julius Sumner Miller: Lesson 13 - Archimedes' Principle

If a body is submerged in a fluid - a liquid or a gas - the body is buoyed up -lifted up - by a force equal to the weight of the fluid displaced. This is the Classic Principle of Archimedes. We show an array of DEMONSTRATIONS bearing on this Principle.
A - We weigh a body on a spring scale. It weighs "so much" . We now
submerge it in a vessel of water. The scale reads less. How much less? We discover this with another demonstration.
B - We now submerge the body in a vessel so the displaced water runs out a spout. We weigh this water which ran out - which was "pushed" out by the body. And what does it weigh? It weighs EXACTLY the very loss in weight the body experienced when submerged. A wonderful thing.
C - So the water in a vessel pushes up on a body submerged in it. Proof: We push a glass into a tank of water. The glass has a hole in the bottom. The water gushes up through the hole.
D - We show a dramatic demonstration of Archimedes' Principle with THE BUCKET AND CYLINDER.
E - As we all know: some bodies sink in water; others float. When does a body float? When it displaces a weight of water equal to its own weight BEFORE it is completely submerged. Thus it is that some wood sinks - other wood floats.
F - Mercury is fantastic stuff! It is very dense. We all know that steel will sink in water. What will steel do in mercury? Answer: Steel will float in mercury.
We show some exciting things in the Life of Archimedes.
1 - A mosaic depicting his death at the hands of a Roman soldier at the
Siege of Syracuse.
2 - A monument to him showing his Burning Mirror.
3 - The classic discovery of the relationship between the volumes of a
cylinder - a sphere - a cone.
4 - A sphere circumscribed by a cylinder - which is what Archimedes wished to have put atop his tomb.
The Life and Work of Archimedes should be read by every student.