Archimedes' Principle 
Archimedes' Principle
by Prof. Miller
Video Lecture 13 of 46
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Date Added: February 5, 2015

Lecture Description

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.

Course Index

  1. The Idea of the Center of Gravity
  2. Newton's First Law of Motion: Inertia
  3. Newton's Second Law of Motion: The Elevator Problem
  4. Newton's Third Law of Motion: Momentum
  5. Energy and Momentum
  6. Concerning Falling Bodies & Projectiles
  7. The Simple Pendulum and Other Oscillating Things
  8. Adventures with Bernoulli: Bernoulli's Principle
  9. Soap Bubbles and Soap Films
  10. Atmospheric Pressure
  11. Centrifugal Force and Other Strange Matters
  12. The Strange Behavior of Rolling Things
  13. Archimedes' Principle
  14. Pascal's Principle: The Properties of Liquids
  15. Levers, Inclines Planes, Geared-wheels and Other Machines
  16. The Ideas of Heat and Temperature
  17. Thermometric Properties and Processes
  18. How to Produce Heat Energy
  19. Thermal Expansion of Stuff: Solids
  20. Thermal Expansion of Stuff: Gases & Liquids
  21. The Strange Thermal Behavior of Ice and Water
  22. Heat Energy Transfer by Conduction
  23. Heat Energy Transfer by Convection
  24. Heat Energy Transfer by Radiation
  25. Evaporation, Boiling, Freezing: A Dramatic Adventure
  26. Miscellaneous Adventures in Heat
  27. The Drama in Real Cold Stuff: Liquid Nitrogen
  28. The Physics of Toys: Mechanical
  29. The Physics of Toys: Acoustic and Thermal
  30. Waves: Kinds of Properties
  31. Sound Waves: Sources of Sound & Pitch and Frequency
  32. Vibrating Bars and Strings: The Phenomenon of Beats
  33. Resonance: Forced Vibrations
  34. Sounding Pipes
  35. Vibrating Rods and Plates
  36. Miscellaneous Adventures in Sound
  37. Electrostatic Phenomena: Foundations of Electricity
  38. Electrostatic Toys, Part 1
  39. Electrostatic Toys, Part 2
  40. Adventures with Electric Charges
  41. Adventures in Magnetism
  42. Ways to "Produce" Electricity
  43. Properties and Effects of Electric Currents
  44. Adventures in Electromagnetism
  45. Further Adventures in Electromagnetism
  46. Miscellaneous and Wondrous Things in E&M

Course Description

Demonstrations in Physics was an educational science series produced in Australia by ABC Television in 1969. The series was hosted by American scientist Julius Sumner Miller, who demonstrated experiments involving various disciplines in the world of physics. The series was also released in the United States under the title Science Demonstrations.

This program was a series of 45 shows (approximately 15 minutes each) on various topics in physics, organized into 3 units: Mechanics; Heat and Temperature / Toys; and Waves and Sound / Electricity and Magnetism.


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