
Lecture Description
A - Since oscillating systems have intimate connection with the production of SOUND we show here a very pretty thing - THE BLACKBURN PENDULUM. A rigid support has two strings fixed to it which join a third to constitute a pendulum of interesting complexion. A funnel hangs as a pendulum bob. We put salt or sand or sugar in the funnel - draw the pendulum aside from its equilibrium position - and let it go. Sand pours out and the pendulum bob executes interesting gyrations. We have here compounded harmonic motions. The result is a figure of great beauty. These figures are called Lissajous Figures.
B - A glass tube has within it a metal rod. This metal rod is damped at its midpoint. In the glass tube we lay out some cork-dust. We now stroke the metal rod with a cloth bearing resin (or rosin) and an amazing thing ensues: The cork dust takes up very unique positions in the glass tube. What happens is this - briefly: The cloth with resin on it grabs the rod and lets go - grabs the rod and lets go — again our relaxation oscillation business. The compressional wave thus generated _m the rod "|umps off" the end of the rod - so to speak - travels to the far end of the glass tube -which is tightly closed with a stopper - and is reflected. This reflected wave or pulse joins hands with the incident wave to give rise to a standing wave - which we see in the configurations the cork dust takes up. And what can we do with all this? Answer: Determine the velocity of sound in the metal rod. This tube is known as Kundt's Tube.
C - An array of bar magnets hanging on strings permits the showing of a
compressional wave advancing. One magnet is pulled aside at the very end of the array and let go. It approaches its neighbor and drives it away - since the plarization is aligned this way. The pulse goes down this array - and suffers reflection from the ."open" end. It can be observed that a change in phase accompanies this reflection.
D - We explore once again the vibrations of high-voltage cables. Dampers are fixed to these cables to reduce the amplitude of oscillation. We show dampers made in the USA - in Germany - in Sweden.
E - The BULL ROARER: A slender strip of wood or masonite is fixed to a string at one end. We swing the strip in a vertical circle. A sound is produced. The strip catches up the air and pushes it to¬gether thus giving rise to a pressure pulse. The effect depends on Bernoulli's Principle - which see in an earlier Lesson in Mechanics.
We close this series on SOUND AND WAVES by showing the CHLADNI PLATES once again for here lies extraordinary beauty and drama. It is this point of view that I urge on all who study anything for then the subject becomes FUN and ENJOYABLE and the SPIRIT is lifted up.
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.