Energy and Momentum 
Energy and Momentum
by Prof. Miller
Video Lecture 5 of 46
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Date Added: February 5, 2015

Lecture Description

It is of great importance that the ideas of ENERGY and MOMENTUM be clearly
distinguished and understood. Mathematically, momentum is M x V or MV.
Energy - more exactly kinetic energy - is 1/2 MV^. We need not worry here
where the 1/2 comes from. Momentum is the consequence of a force acting for
a time: F x t. Energy is the consequence of a force acting over a distance: ___
Thus it is with the two cars:
The force acting on both cars is the same. The force acts for the same time on both. The force acts for a greater distance on the little car and for a lesser distance on the bigger car.
Accordingly: The F x t is the same for both.
Therefore their momenta are equal. The F x S for the little car is greater than the F x s for the bigger car. Therefore their energies are UNequal.
We show an array of DEMONSTRATIONS bearing on ENERGY and MOMENTUM.

1 - On a curved track the ball can go no higher to a remote end than the height
from which it was released.

2 - We drive a nail into a block of wood. The energy delivered to the system
by the moving hammer is spent in splitting the wood and raising the temperature of the nail and the wood. Friction always produces heat.

3 - We demonstrate acoustic energy which arises from the mechanical energy
of my moving vocal cords.

4 - Thermal energy communicated to a kernel ,of corn makes it "pop" . The
expansion of the water in the corn is enormous.

5 - We rub a rod of bakelite (hard-rubber) with a piece of fur. This mechanical
work separates the electric charges and "creates" electrostatic energy.

6 - A pile-driver delivers the potential energy of the driver to the nail.

7 - A spring is compressed; potential energy is stored. This energy can push
a ball upward when the spring "recovers" .

8 - In shooting a gun we hold it tightly against the shoulder so the "kick"

9 - A child's toy stores "elastic" energy in a wound-up rubber band. This
stored energy can drive the car backwards.

10 - A geared-wheel is turned by mechanical force. The energy thus stored can heat a metal to incandescence - that is - hot enough to emit light, Thus mechanical energy produces heat and light.

We show a likeness of Christiaan Huygens, a Dutchman, who contributed to our understanding of these things.

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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