Forces and Their Representation

Look back at your prior definition of "force." How close was your definition to the one used in physics? At this point, you should understand that a force is anything that pushes, pulls and/or has the ability to cause an object to change its motion.

Forces come in two general categories: Contact forces, which require two or more objects to be touching, and action-at-a-distance forces which can act when objects are not touching. The forces you will most commonly encounter in physics are the gravitational force, the normal force, applied forces, tension and friction. Later in the course, you will also be considering the electromagnetic force.

Mass and weight differ, in that, mass is a measure of inertia as well as how much matter is contained in an object; thus, it stays the same regardless of location. The weight of the object is a result of the gravitational force acting on the object; therefore, it will vary greatly based on the object's location in the universe. You represent forces using a free body diagram, where arrows show the magnitude and direction of each force acting on an object. This helps you to calculate the net force acting on an object.

For more information on forces view the video clip Scalars and Vectors from Discovery Education™ streaming.