How to Draw Free Body Diagrams

First of all, it is important to know what a free-body diagram is.

Note the distinction between the two very similar options above. First of all, let us follow the standard steps for drawing such a diagram.

Step 1. Identify the object you will draw a diagram for. A free-body diagram must be done for one object only, since it represents the forces applied on that object alone. If you are interested in all the forces on a set of $n$ objects, you must draw $n$ free-body diagrams.

Step 2. Identify all the forces on the object. If you know where the forces are coming from, great, but it's not relevant to drawing the diagram.

Step 3. Draw arrows for each force pointing in the appropriate direction $-$ remember, forces are vectors! It is often convenient to draw the arrows from the point of contact. For example, the force is gravity is drawn from the center of mass of the object (if you are giving the object a shape in the diagram) downwards.

At this point, you are basically done, congratulations! From here, if you are interested in particular components of some forces, you should draw the component vectors in a different color or with dotted arrows as opposed to the solid arrows that you used to draw the resultant force vectors.

Free body diagrams provide physicists with pictorial representations of all the forces acting on an object. First, identify an inertial frame of reference. Given a diagram or scenario, label the item for which you will be drawing a free body diagram for. Treat the object as a point particle, representing the object as a dot in your free body diagram. This object is the system you are analyzing. Next, draw all the forces acting on the object as arrows. Make sure that the length of the arrows represent the magnitude of the force acting on the object, and make sure that the arrows point in the correct direction. Since forces are vector quantities, it is of the utmost importance that one correctly specifies both magnitude and direction.

The free body diagram for the question would look like the following: