上浒充通大￥ 4.2 Indroduction to Pressure Shanghai Jiao Tong University Pressure always acts inward normal Pressure to any surface. Body Pressure is a normal stress,and hence has dimensions of force per unit area,or [ML-1T-2]. In the Metric system of units,pressure is expressed as "pascals"(Pa)or N/m2. △Fn Standard atmospheric pressure is 101.3 kPa. Surface Pressure is formally defined to be △A lim △Fn △A→0△A where AF is the normal compressive force acting on an infinitesimal area4Shanghai Jiao Tong University 4.2 Indroduction to Pressure Pressure always acts inward normal to any surface. Pressure is a normal stress, and hence has dimensions of force per unit area, or [ML-1T-2]. In the Metric system of units, pressure is expressed as "pascals" (Pa) or N/m2. Standard atmospheric pressure is 101.3 kPa. 0 lim n A F p Δ → A Δ = Δ Pressure is formally defined to be where ΔF n is the normal compressive force acting on an infinitesimal area . ΔA