Body force
A body force is a force that acts throughout the volume of a body. Gravity and electromagnetic forces are examples of body forces. Inertial spin forces such as the Centrifugal force, Euler force, and the Coriolis effect are also examples of body forces.
This can be put into contrast with contact forces or the classical definition of surface forces which are supposed to be exerted to the surface of an object. Shear forces and normal forces occurring in physical and engineering circumstances are supposed to be surface forces and exerted to the surface of an object. All cohesive surface attraction and contact forces between objects are also considered as surface forces.
A body force is simply a type of force, and so it has the same dimensions as force, [M][L][T]−2. However, it is often convenient to talk about a body force in terms of either the force per unit volume or the force per unit mass. If the force per unit volume is of interest, it is referred to as the force density throughout the system.
A body force is distinct from a contact force in that the force does not require contact for transmission. Thus, common forces associated with pressure gradients and conductive and convective heat transmission are not body forces as they require contact between systems to exist. Radiation heat transfer, on the other hand, is a perfect example of a body force.
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