Some Physics You Need to Know

Abstract

Mass, length, and time are concepts basic to all physics. In physics we measure them respectively in units of kilograms, meters, and seconds. Although these units have been very precisely defined by an international committee, there are approximate definitions of these units that are more useful for you to know: A mass of one kilogram is the mass of a liter of water, a little more than a quart; one meter is about the length between your nose and the end of your fingers when your arm is stretched out to the side; one second is about to the time between your heart beats when you are at rest. In what follows we will look at useful ways to understand the magnitudes of units and see how to create new ones to describe and measure velocity, acceleration, momentum, force, and energy. Most of the units used in this book are part of the internationally agreed-upon Système International (SI). There is a good summary of SI units at the end of the book.