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.
Pennyweight (pwt)
The pennyweight (pwt) is a unit of mass traditionally used in the precious metals and jewelry industries. It is part of the troy and apothecary weight systems.
One pennyweight equals 1/20 of a troy ounce, or 24 grains, which is approximately 1.555 grams.
Pennyweights are commonly used to measure gold, silver, and gemstones, offering a precise small-scale weight unit for valuable materials.
Summary:
1 pennyweight = 1/20 troy ounce ≈ 1.555 grams
Used mainly in precious metals and jewelry
Part of the troy weight system