The Physics of Toys: Acoustic and Thermal 
The Physics of Toys: Acoustic and Thermal
by Prof. Miller
Video Lecture 29 of 46
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Date Added: February 5, 2015

Lecture Description

This video is incomplete. Other copies exist on the internet--search for them if necessary.

A. We explored in another LESSON - on MECHANICAL TOYS -
the behavior of the TOY GUN which projects a pingpong ball.
Another question arises in this toy: When the ball is "fired" we
hear a "pop". A "poop". Where does THIS arise? Where does
the sound come from? So we see that this toy is not merely mechanical but gives rise to a question in ACOUSTICS. And the pitch of the "poop" can be altered by squeezing tightly or less so. . .suggest¬ing that it is the expanding air that emerges which gives rise to the sound. Much more can be said about this.

B. A disc - like a small saucer - has holes m rt. Another like it
is fitted to the first at their faces. We spin these on a string. We
are storing elastic twist energy in the wound-up string. On unwinding the "musical" system emits a pleasant array of sounds. . . .
the result of air rushing into and out of the holes. AND - what
do we see on the string? We see some standing waves set up. If
we examine this standing-wave mechanism closely we can relate
the wavelength on the string to the pitch of the note emitted. Beautiful thing.

C. Another musical device like that in B is made up of two hemispheres
face to face - with holes in each. The pitch emitted is different
- the rotational speed different - the mechanical properties of a disk different from the mechanical properties of a sphere.

D. An airplane on a string is swung round and round - the other end
of the string fitted to the shaft of a stick held in the hand. And we
hear strange things! The string on the shaft is grabbed and let go -
grabbed and let go - like a violin bow grabbing the string on the
fiddle and letting go — relaxation oscillations - we call this.
Thus it is that the nose of the airplane is pulled out and relaxed -
pulled out and relaxed - and since it is flexible the air around
it has pulses delivered to it.

E. Another device of like nature: A winged insect. But here the
creature has a hollow chamber. And so what can we do? We first
listen to the note emitted with the chamber open then we close the
chamber with a cork stopper. And the note is changed because
open pipes and closed pipes emit different pitches.

F. The Bird Whistle: A chamber has a sliding piston. Its length can
thereby be changed. The pitch can thus be changed. Now too we
can heat the chamber whereupon the pitch changes. Thus we see
how length of pipe and temperature affect the pitch emitted. So
in orchestras: The temperature goes up - the stringed instruments
get lower - the winds get higher. Watch for this when next you
listen to an orchestra.

G. The Xylophone: An array of metal strips is fixed to "runners". The
metal strips are fastened at unique points - nodes. The strip is
struck with a tiny hammer. Each emits a note governed by its length
- its size - its thickness - its stuff.

H. Two Frogs: A metal frog has a highly elastic flexible metal strip fixed to his body underneath. We flex the metal strip. What we hear is governed by the geometry and mechanical properties of the strip. The heavier the strip the greater the inertia and - in general
- the lower the sound emitted.

I. A spinning wheel has a low-melting point metal fixed to it. The
mechanical energy delivered by the hand turns the wheel which scrapes the metal which heats it to incandescence which gives light. So we have the conversion of several kinds of ENERGY. . . mechanical - thermal - optical.

J. A Pop Gun: A long cylindrical chamber has a stopper closing one end. We drive a piston into the cylinder. Out pops the stopper and we hear a "poop". The longer the chamber the lower the pitch.

K. We show several other ACOUSTIC TOYS thus revealing the beauty and drama in things which are essentially for child's play but in which reside really rough and troublesome PHYSICS PRINCIPLES.

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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