In physics, a free body is an object that is isolated from its surroundings and is being analyzed in terms of the forces acting upon it. A free-body diagram is a graphical representation of the forces acting on a free body. It is a pictorial device used by physicists and engineers to visualize the applied forces, moments, and resulting reactions on a body in a given condition .
Free-body diagrams are used to show the relative magnitude and direction of all forces acting upon an object in a given situation. They are a special example of the vector diagrams that were discussed in an earlier unit. These diagrams will be used throughout our study of physics . The size of the arrow in a free-body diagram reflects the magnitude of the force. The direction of the arrow shows the direction that the force is acting. Each force arrow in the diagram is labeled to indicate the exact type of force. It is generally customary in a free-body diagram to represent the object by a box and to draw the force arrow from the center of the box outward in the direction that the force is acting .
Free-body diagrams are used to solve problems involving forces acting on an object. To construct a free-body diagram, it is extremely important to know the various types of forces. If given a description of a physical situation, begin by using your understanding of the force types to identify which forces are present. Then determine the direction in which each force is acting. Finally, draw a box and add arrows for each existing force in the appropriate direction; label each force arrow according to its type. There is no hard and fast rule about the number of forces that must be drawn in a free-body diagram. The only rule for drawing free-body diagrams is to depict all the forces that exist for that object in the given situation .
In summary, a free body is an object that is isolated from its surroundings and is being analyzed in terms of the forces acting upon it. A free-body diagram is a graphical representation of the forces acting on a free body. Free-body diagrams are used to show the relative magnitude and direction of all forces acting upon an object in a given situation. They are a special example of the vector diagrams that were discussed in an earlier unit. These diagrams will be used throughout our study of physics. To construct a free-body diagram, it is extremely important to know the various types of forces. If given a description of a physical situation, begin by using your understanding of the force types to identify which forces are present. Then determine the direction in which each force is acting. Finally, draw a box and add arrows for each existing force in the appropriate direction; label each force arrow according to its type .