Surface force

Block on a ramp and corresponding free body diagram of the block showing the surface force from the ramp onto the bottom of the block and separated into two components, a normal force N and a frictional shear force f, along with the body force of gravity mg acting at the center of mass.

Surface force denoted f_s is the force that acts across an internal or external surface element in a material body. Surface force can be decomposed into two perpendicular components: normal forces and shear forces. A normal force acts normally over an area and a shear force acts tangentially over an area.

Equations for surface force

Surface force due to pressure

f_{s}=p\cdot A\

, where f = force, p = pressure, and A = area on which a uniform pressure acts

Examples

Pressure related surface force

Since pressure is ${\frac {force}{area}}={\mathrm {{\frac {N}{m^{2}}}}}$ , and area is a $(length)\cdot (width)={\mathrm {m\cdot m}}={\mathrm {m^{2}}}$ ,