Its connection with equine work capacity is tenuous. A human being can apparently work at a rate of about .35 horsepower for short periods of time, if all their skeletal muscles are being effectively used. Thus, a body acted on by a 0.5 g acceleration experiences a force equal to half its weight. This force acts in the direction of the acceleration. Frequently, during high speed collisions, accelerations in the range of 25 to 50 g's are generated.
Pressure is force per unit area.
Thus, if a 10-lb. Thus, a 30-inch column of mercury weighs about as much as 80 miles of air since they both exert the same weight force per unit area. Stress, like pressure, is also a force per unit area. However, while pressures acts on bodies, stresses act in a body. If I pull on both ends of a steel bar of 1 in. cross-sectional area with a force of 100 lbs., I generate a tensile stress inside the bar of 100 psi .