Is the Pound a unit of mass or force in the US?
In the US, the formal unit for mass is slug. It is rarely used. The formal unit for force is pound. It is noted as lb or if there is confusion lb (f), with (f) denoting a subscript “f.” It is very common in the US to use a contrived unit for mass known as the pound -mass. This has units of lb (m). One lb (m) when accelerated by gravity gives rise to one lb (f). When a person is weighed on a scale, the reading is in pounds. The scale reads a force, lb (f). The mass of the person is the mass-equivalent ,lb (m).
