I.2 The Science of Physics

 Physics is most often divided up into 5 disciplines:

·         Mechanics, which is concerned with the effects of forces on objects (which will be the main focus of this class).

 ·        Thermodynamics, which deals with heat, temperature changes and the effects on the large number of particles.

 ·        Electromagnetism, which deals primarily with currents, magnetic charges, and electromagnetic fields.

 ·        Relativity, a theory connected to moving particles with a speed close to the speed of light, and relationship of time and space.

 ·         Quantum Mechanics, a theory dealing with the behavior of submicroscopic particles.

 I.2.1 Mechanics

 Aristotle and Galileo: The study of gravity

Aristotle was one of the first to describe motion of objects. One of his studies included the study of how things fall. Aristotle determined that downward speed of an object is determined by both the medium through which it falls and (most importantly) the weight. This position, that lighter objects fall more slowly and vice versa, was considered valid for about 2000 years.

 However, such noted astronomers as Copernicus and Galileo achieved great advances in mechanics during the 16th and 17th centuries. Galileo performed his own studies, some of which involved dropping objects from the Leaning Tower of Pisa, and determined that the long-standing beliefs about gravity were untrue. Galileo determined that objects of any weight would fall at the same speed, if air friction is neglected.

 Sir Isaac Newton

It was Sir Isaac Newton (the great modern day genius) who later made major development that governs the mechanics (motion) of physical objects to date. In 1687, Sir Isaac Newton published Principia, which was based on his notion of universal gravitation. (falling apples and such). Today, mechanics is a part of our everyday life, and is used for scientific, recreational and safety purposes.

 The Acceleration due to Gravity:

The formula, (obtained from Eq. (3) page 4,)  can be used to find the distance (d), acceleration (a), or time (t) of an object if the other two variables are known.

 The acceleration due to gravity can be found to be 32 feet per second per second (32 ft/sec²). This converts to roughly 9.8 meters per second squared which we will round up to 10 meters per second squared for class purposes. Acceleration due to gravity is always downward, toward the earth.