Centrifugal Force and Other Strange Matters 
Centrifugal Force and Other Strange Matters
by Prof. Miller
Video Lecture 11 of 46
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Date Added: February 5, 2015

Lecture Description

The name "centrifugal" force given to certain events is very often badly used. Consider a car going round a curve. A book lies on the seat beside you. You are the driver. You take a curve to the left - say. As you make the curve you see the book move radially out on the seat - moving toward the door. NO! This is not right! You make the curve. The car makes the curve. The book keeps on going in a straight line - tangent to the curve. It does not move radially outward. We show some DEMONSTRATIONS on these matters.

A - We whirl a ball on a string in a vertical circle. At the top of the
circular path we let go of the string. What does the ball do? Does it go radially outward? NO. It goes off in the direction it was going -tangent to the path. This is Newton's First Law again. See Program *2.

B - A device has two spheres in it - lying in a circular trough. To get each
sphere to ITS end of the trough we spin the device about a central vertical axis. The balls get to their respective slots at the ends but they do not fly radially outward.

C - IN THE PARADOX OF THE ROTATING CANDLES we spin the apparatus about a central vertical axis - as in B above - but this time a paradox arises. The candle flames lean INWARD. HINT: The density - the "heaviness" of the flames - is less than that of the air in the protecting chimneys.

D - In the classic of whirling a bucket of water in a vertical circle it is always said: " If you don't go fast enough the water will fall out" . NO. This is not right. For when the motion is too slow to make the circle the bucket will fall along with the water! OK?

E - On the forces which arise in rotation we show: (a) Why the Earth is flattened at the Poles; (b) How a "governor" works; (c) A coin on a coat-hanger; (d) A String in a Glass Tube; (e) A limp rubber loop rolls off as a rigid body; (f) A lasso; (g) Emptying a jug of water in the quickest way.

We raise an added dilemma with a toy gun which "rolls" a hoop away and then — e -coo "rolls" back! Question: How can a hoop ROLL AWAY - rolling in one direction - and roll back - still rolling? ANSWER: It can not! So - if we look circumspectly at the Physics of this we discover an enchanting thing.

The hoop was NOT rolling away - Got it?
NOTE: This business of Centrifugal Force is very troublesome for beginners -indeed for everybody. What we see happen in circular motion really depends upon where the observer is. Which brings us to the subject of Relativity.

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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