Question

what is the purpose of a free body diagram?
to show the velocity of an object
to show the acceleration of an object
to show the forces acting on an object
to show the direction of motion vectors of an object

Explanation:

A free - body diagram is a tool in physics that isolates an object and shows all the external forces acting on it. It does not represent velocity, acceleration, or direction of motion vectors directly. Its main focus is forces.

Answer:

to show the forces acting on an object