3 Fundamental Concepts in Engineering – Basic Quantities and Newton’s Laws
3 Fundamental Concepts in Engineering – Basic Quantities and Newton’s Laws
Let us start off with a brief review of certain fundamental concepts and principles.
In this course it is assumed that you have completed a basic physics class in your secondary school. If you need more information, I recommend that you refer to two open source textbooks. OpenStax College Physics is an algebra-based book. https://openstax.org/details/books/college-physics OpenStax University Physics is a calculus-based textbook. https://openstax.org/details/books/university-physics-volume-1 I will be using some examples and images from them in this book but I encourage you to look them over before and maybe during this course.
Basic Quantities
The following four quantities are used when we talk about mechanics. They are often called “base units” as other units can be made by combining the base units.
Length. Length is used to locate the position of a point in space. It describes the size of a certain physical system. Once you have length, you can have area and volume.
Time. Time is the indefinite continued progress of existence and events that occur in an apparently irreversible succession from the past, through the present, into the future.
Mass. Mass is a measure of the quantity of matter. It is defined by its inertia, its resistance to being accelerated, and by the gravitational attractions that occurs between two bodies.
Force. Forces are considered to be pushes or pulls exerted by one body on another body. It can occur due to direct contact when two bodies touch or there can be action at a distance such as the gravitational, magnetic and electric forces. Forces are vectors and is characterized by its magnitude, direction and the point where it is applied.
Models or Idealizations
Models, or idealizations, are used in science in order to simplify applications of theories. Here are three main idealizations we will use in this textbooks. There is an aphorism, often attributed to George Box a statistician that goes “all models are wrong, but some are useful.”
Particle. A particle has a mass, but the size can be neglected. This often depends on the system. As we stand on the Earth we are aware that is it not a particle. Yet when we consider the Earth orbiting around the Sun we treat it as a particle because with a radius of 6378 km and the semi-major axis of the orbit being 149,596,000 km the means that the Earth’s radius is only 0.004% of the orbital distance so it is reasonable to consider it a particle when we deal with orbits. We reduce things to particles to simplify the analysis as the geometry of the object will not be involved in the analysis.
Rigid Body: A rigid body can be considered to be a combination of a large number of particles where all the particles remain at the same distance from each other, even when a large force or load is applied to the body. The shape does not change. In most cases the actual deformations that occur when a body is forced is relative