Forces and Their Representation

Forces and Gravity

In this presentation, you will apply the physical definition of force in order to predict how forces combine when acting on an object. Next, you will investigate gravitational force, and understand the difference between mass and weight. In addition, you will learn how to represent multiple forces in a free body diagram to determine the net force acting on an object. Finally, you will analyze multiple applications of forces and follow step by step examples used in calculations. At the conclusion of the presentation, you will apply what you have learned in an interactive problem-solving exercise. Click the player button to begin.

View a printable version of this interactivity.

 

Free Body Diagrams

When drawing and labeling free body diagrams (FBD’s), there are several commonly used sets of notation and subscripts preferred by different teachers, professors and textbooks.  For example, the gravitational force can be labeled as “mg”, “F_g” or “F_W”.  These three are equivalent and equally correct.  Similarly, the normal force is either labeled as “F_N” or simply as “N” and tension will be found labeled either as “F_T” or simply as “T”. In this course, for consistency, the choice was made to label each force using a capital “F” and a subscript denoting the type of force.

When discussing gravitational force in this course, it’s important to emphasize the difference between the acceleration of gravity and the force of gravity. “F_W” will be used to label the gravitational force, as the force of gravity is equivalent to the weight of the object.  The exception to this is when dealing with universal gravitation, where “F_G” will be used.

 

Forces and Gravity Practice

Now, practice your knowledge of net forces, gravitational force, differentiation between mass and weight, and drawing free body diagrams by completing the interactivity below. Click submit after answering each question. Click the player to started.