Convert Poundal (pdl) to Pound-force Square Second/Foot (lbf·s²/ft) instantly.
About these units
Poundal (pdl)
The poundal is the unit of force in the foot–pound–second (FPS) system, defined as the force that accelerates a one-pound mass at one foot per second squared. Although a force unit, it interacts with mass units in engineering contexts similarly to inertial mass units. Historically, poundals appeared in older physics textbooks and engineering references before the widespread adoption of SI units. Their use has declined dramatically, but they remain part of the history of classical mechanics education. The poundal exemplifies how many different systems attempted to rationalize force, mass, and acceleration before the international community converged on the SI newton.
Pound-force Square Second/Foot (lbf·s²/ft)
This unit is part of the British Gravitational System, where mass is defined from force rather than the other way around. It can be interpreted as an inertial mass unit, since applying 1 pound-force to it would produce an acceleration of 1 foot per second squared. Historically, before the SI system clarified the distinction between force and mass, engineering fields often used mixed systems where pounds could represent either force (lbf) or mass (lbm). The unit lbf·s²/ft was introduced to straighten out these ambiguities in dynamic calculations such as impact forces, mechanical oscillations, and safety load computations. Today, the unit survives mostly in engineering textbooks, legacy calculations, and historical documentation. It demonstrates how complex and inconsistent measurement systems once were, and why global scientific communities moved toward SI clarity.