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.
Gamma
The gamma (γ) is a very small unit of mass used mainly in geophysics, soil science, and radiology. It is equivalent to one microgram (1 µg) or 10⁻⁶ grams.
The term "gamma" is often used to express trace amounts of substances or contaminants in samples, helping scientists measure extremely small quantities with precision.
Summary:
1 gamma = 1 microgram = 10⁻⁶ grams
Used in soil science, geophysics, and radiological measurements
Ideal for quantifying very tiny masses