Ramblings

Massing or Weighing

A while back, a friend used the term massing to determine the mass of an object using a scale. At the time, I thought this was a rather strange choice of words, but left it at that as I understood what she meant. Recently, my mind wandered back to the topic and I decided that the term is incorrect. When using most measuring devices on Earth, gravity is required to determine mass.

According to Newton's second law, F = ma. Now on the Earth, weight (W) is the force applied to a body by gravity (g). So W = mg. Rearranging this gives m = W/g.

Most measuring devices therefore measure weight, not mass, and convert this to mass using an assumed value of g. Single pan laboratory scales are calibrated by using weights of known mass. Two pan chemical balances use weights of known mass to balance the weight of the unkown sample as gravity acting equally on both pans.

The determination of mass thus always relies on gravity, either explicitly or implicitly. The use of the term massing is therefore incorrect.

(31 December 2025)