
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
- The Idea of the Center of Gravity
- Newton's First Law of Motion: Inertia
- Newton's Second Law of Motion: The Elevator Problem
- Newton's Third Law of Motion: Momentum
- Energy and Momentum
- Concerning Falling Bodies & Projectiles
- The Simple Pendulum and Other Oscillating Things
- Adventures with Bernoulli: Bernoulli's Principle
- Soap Bubbles and Soap Films
- Atmospheric Pressure
- Centrifugal Force and Other Strange Matters
- The Strange Behavior of Rolling Things
- Archimedes' Principle
- Pascal's Principle: The Properties of Liquids
- Levers, Inclines Planes, Geared-wheels and Other Machines
- The Ideas of Heat and Temperature
- Thermometric Properties and Processes
- How to Produce Heat Energy
- Thermal Expansion of Stuff: Solids
- Thermal Expansion of Stuff: Gases & Liquids
- The Strange Thermal Behavior of Ice and Water
- Heat Energy Transfer by Conduction
- Heat Energy Transfer by Convection
- Heat Energy Transfer by Radiation
- Evaporation, Boiling, Freezing: A Dramatic Adventure
- Miscellaneous Adventures in Heat
- The Drama in Real Cold Stuff: Liquid Nitrogen
- The Physics of Toys: Mechanical
- The Physics of Toys: Acoustic and Thermal
- Waves: Kinds of Properties
- Sound Waves: Sources of Sound & Pitch and Frequency
- Vibrating Bars and Strings: The Phenomenon of Beats
- Resonance: Forced Vibrations
- Sounding Pipes
- Vibrating Rods and Plates
- Miscellaneous Adventures in Sound
- Electrostatic Phenomena: Foundations of Electricity
- Electrostatic Toys, Part 1
- Electrostatic Toys, Part 2
- Adventures with Electric Charges
- Adventures in Magnetism
- Ways to "Produce" Electricity
- Properties and Effects of Electric Currents
- Adventures in Electromagnetism
- Further Adventures in Electromagnetism
- 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.