A mechanical force involves contact with another object. Mechanical forces are distinguished from the four natural forces of electromagnetism, the strong nuclear force, the weak nuclear force and gravity. While each of the four natural forces do not require a physical connection, mechanical forces must travel through a medium.
An example of a mechanical force is someone pushing a door. The person’s hand makes direct contact with the door and applies the force to it. By contrast, if the door is not perfectly level, gravity pulls it in one direction or the other without making direct contact with it. Mechanical forces can travel through the air as the air functions as a medium, but natural forces can travel through space, which is not a medium.