is pounds a unit of force or mass
Pound (force) The pound-force (symbol: lbf[1], sometimes lbf,[2]) is a unit of force used in some systems of measurement including English Engineering units and the British Gravitational System.[3] Pound force should not be confused with foot-pounds or pound-feet, which are units of torque, and may be written as "lbf⋅ft". They should not be confused with pound-mass (symbol: lb), often simply called pounds, which is a unit of mass.
Mass–energy equivalence In physics, massâ€“energy equivalence states that anything having mass has an equivalent amount of energy and vice versa, with these fundamental quantities directly relating to one another by Albert Einstein's famous formula:[1]