Chapter 1

An Introduction to Physics

What is Physics?

Physics is the quantitative study of property and behavior of the material world in the universe.

For example: what is air made of? Why is the sun hot and bright? What are the property of a moving object? How do moving objects interact? ..... etc.

Laws of Physics are quantitative relationships based on observations of a class of phenomena occuring in the physical world.

Theory is an explanation of an observed phenomenon. A useful theory must lead to predictions that can be tested by observations for improvement.

All theories are tentative and incomplete.

Nature reveals itself through an iterative process in which theories predict and experiments dictate.

Measurements:

Quantitative study requires measurements. The three fundamental measurements in physics are:

Length, Mass, and Time

In the metric system of units: length is measured in meters, mass in kilograms, and time in seconds. This is the MKS units.

We will talk about measurements and units throughout our discussion of physics. I will talk about each as they come up

Some simple unit conversions will be left as homework problems.

HW Chapter 1 --- P7, P13, P19 --- "P" stands for problems listed at the end of each chapter in your textbook. Hence P7 is problem #7; P13 is problem #13, ..... etc.

 A Brief History of Newtonian Mechanics

  • 340 B.C. Greek Philosopher Aristotle put forth an argument for believing that the earth is a round sphere rather than flat plate.
  • In the second century (between 100-200 A.D.), Ptolemy proposed a earth-centered cosmological model: the earth stood at the center, surrounded by the moon, the sun, the stars, and 5 planets known at the time: Mercury, Venus, Mars, Jupiter, and Saturn.
  • In 1514, a Polish priest, Nicholas Copernicus, proposed a sun-centered cosmological model in which the sun was stationary at the center and the earth and other planets moved in circular orbits around the sun. This model was supported by two astronomers Johannes Kepler and Galeleo Galilei.
  • In 1609, Galileo, using his newly invented telescope, found several satellites or moons orbiting around Jupiter.
  • Around this time, Kepler modified Copernicus' theory, suggesting that the planets move not in circles, but in ellipses.

  • In 1687, Issac Newton published perhaps the most definitive single work in the physical sciences.