3.6 Introduction to Electric Forces

Introduction to Electric Forces

• First Law of Motion: An object will remain at rest or in motion at a constant velocity unless acted upon by an external force. This is often referred to as the law of inertia.
• Second Law of Motion: The acceleration of an object is directly proportional to the force applied to it and inversely proportional to its mass. This can be written as F = ma, where F is the force applied to the object, m is the mass of the object, and a is the acceleration of the object.
• Third Law of Motion: For every action, there is an equal and opposite reaction. This means that if two objects interact, they will exert equal and opposite forces on each other.

Newton's First Law

• Newton’s First Law states that “every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it." ⬅️➡️

• Inertial Mass—mass that is accelerated (mass in motion)

• Gravitational Mass—mass based on an object’s weight (mass being pulled by the gravitational field)

Newton's Second Law

• Newton’s Second Law states, “The acceleration of an object as produced by a net force is  to the magnitude of the net force, in the same direction as the net force, and to the mass of the object.”

• Key equation: Force = mass x acceleration (F=ma)

Newton's Third Law

• Newton’s Third Law states that

• In other words, an object cannot exert a force on itself.

• Action-Reaction Pair: The force exerted on an object is the action, and the force experienced by the object is the reaction. Action-Reaction pairs occur only when two objects interact. (Example: a book pulling down on a table <-> a table pushing up on a book.)

Electric force at work! Paper sticking to comb!

History and Introduction of Electric Forces

• The ancient Greeks, including philosophers such as Thales and Aristotle, observed that certain materials, such as amber, could attract small objects when they were rubbed with fur. This phenomenon, known as triboelectricity, was one of the first known examples of electric forces.
• In the 16th and 17th centuries, scientists such as William Gilbert and Francis Bacon conducted experiments and made observations about electric forces and magnetism. Gilbert is credited with coining the term "electricity" and developing the concept of electric charge.
• In the 18th century, the work of scientists such as Benjamin Franklin and Charles-Augustin de Coulomb laid the foundations for our modern understanding of electric forces. Franklin's experiments with lightning rods helped to demonstrate the nature of electric charge and the concept of grounding. Coulomb developed Coulomb's Law, which describes the electrical force between two charged particles.
• In the 19th and 20th centuries, the study of electric forces continued to advance, with contributions from scientists such as James Clerk Maxwell, who developed a mathematical theory that united electricity, magnetism, and light, and Michael Faraday, who developed the concept of the electromagnetic field.
• Today, our understanding of electric forces continues to evolve and develop through ongoing research and experimentation by scientists and engineers around the world