3.3 Forces in a Free-Body Diagram
External forces acting on an object may include friction, gravity, normal force, drag, tension in a string, or a human force due to pushing or pulling.
Suppose a book is pushed over the surface of a table top. How can we represent the forces acting on the body using a free-body diagram?
lightbulbFree-body diagrams are used to show the relative magnitudes and directions of all the forces acting on an object in a given situation. In other words, a free-body diagram is a special example of vector diagrams.
Usually, the object is represented by a box, and the force arrows are drawn outward from the centre of the box in the directions of the forces. The length of a force arrow reflects the magnitude of the force, and the arrow head indicates the direction in which the force acts. Each force is labelled to indicate the exact type of force.