What is Mass?

Mass measures the amount of matter in an object. Unlike weight — the force gravity exerts on that mass — mass is absolute: a 10 kg bowling ball stays 10 kg on Earth, in space, and on Jupiter, while its weight changes everywhere. The standard unit is the kilogram.

Three Ways to Find It

From density, m = ρV — the everyday route for objects and materials. From force, m = F/a — Newton's second law, used when you measure how hard something accelerates. From energy, m = E/c² — Einstein's equivalence, where a hair's worth of mass releases staggering energy.

Choosing a Method

Use density when you know the material and its size; use force when you can measure push and acceleration; use energy only for nuclear-scale phenomena. All three return the same physical quantity — mass — in kilograms, with the other units shown for convenience.