What is a Free Body Diagram?
A Free Body Diagram is a diagram that simplifies a component or system of components to the loads and moments applied to them. A Free Body Diagram is required to find and evaluate different forces acting on a body whenever it is in equilibrium. These diagrams are widely used to compute internal forces within a building as well as to determine the loading of particular structural components.
The Free Body Diagram plays a very important role in visualizing and calculating resultant forces. The interaction forces and/or moments assigned to the now opened-up body must follow Newton’s Third Law. The body of interest and the external forces operating on it is represented by an FBD.
- The body: Depending on the type of body (particle/ extended, rigid/ non-rigid), and the questions to be addressed, this is generally a schematic.
- External forces: It is denoted by arrows with labels. A force arrow might indicate the path of action and its direction, the magnitude, and the application point.
Essential Characteristics of Free Body Diagram
Students can use a Free Body Diagram to envision an issue in its entirety or to understand a specific element of a more complex problem. So, in a nutshell, FBD is a fantastic tool for visualizing and solving engineering challenges.
There are some important points regarding Free Body Diagrams. A Free Body Diagram is a diagram or sketch of the selected system or body isolated from the surroundings. The system is shown completely isolated from all the other bodies including the foundation, support, etc. Interaction in the system by each body is removed in the isolated system.
Steps Involved in Drawing a Free Body Diagram
Free-body diagrams depict the magnitude and direction of all forces operating on an item in a given condition. The amount of the force is represented by the size of the arrow in a free-body diagram. The arrow indicates the direction in which the force is acting. Each force arrow in the diagram is identified with the sort of force it represents.
First of all selection of a system is necessary. Then, we need to identify all the forces acting on the isolated body or system. We need to choose the direction of forces and coordinate system. Resolve the forces along these axes and write the equilibrium equations. After writing all the necessary equilibrium equations, we need to find out the required unknown forces.
Advantages of a Free Body Diagram
Drawing a free-body diagram is a crucial step in addressing mechanics issues because it allows you to see all of the forces operating on a single item. In order to apply Newton's Second Law to the motion of an item, the net external force acting on it must be determined.
There are many advantages of drawing Free Body Diagrams. It is a medium to convert ideas into a physical model. It also helps in understanding all facts of a problem. It assists to build up suitable mathematical equations between various forces acting upon a link.
While drawing the Free Body Diagram, all the supports of the body are removed and replaced with reaction forces acting on it.
Simply Supported Beam
Equations of Equilibrium
∑Fx = 0
∑Fy = 0
∑M = 0
Free Body Diagram Problems
- Two bodies of masses 10kg and 20kg are connected together with the help of string are placed on a horizontal smooth surface. The body of 10kg is pulled by 600N force. Find the Tension in the string. (Ans – 400N)
- Find the tension in three strings A, B & C from the below-given figure.
(Ans – TA = 400N, TB = 500N & TC = 300N)