Slug
The slug is a unit of mass used primarily in the U.S. customary system and British engineering contexts.
1 slug = 32.174 pounds (lb) (mass)
Equivalent to approximately 14.5939 kilograms (kg)
Defined so that when a force of one pound-force (lbf) acts on a mass of one slug, it accelerates at 1 ft/s² (using F=ma in imperial units).
Key Facts:
Used mainly in physics and engineering for calculations involving Newton’s second law in imperial units
Allows consistent use of pound-force and pound-mass without extra conversion factors
Useful in dynamics, ballistics, and engineering mechanics
The slug bridges the gap between force and mass in the imperial system, making calculations easier when using pound-force units.
Kip
The kip is a unit of force commonly used in engineering, especially in the United States.
1 kip = 1,000 pounds-force (lbf)
1 kip ≈ 4,448.22 newtons (N)
Symbol: kip
Key Points:
Used to measure large forces or loads, such as in structural engineering, construction, and material testing
Simplifies the expression of heavy loads (e.g., instead of 20,000 lbf, engineers say 20 kip)
Part of the U.S. customary system, not an SI unit
The kip is widely used in practice where large forces are common, making calculations and communication easier.