<P> In commercial and everyday use, the term "weight" is usually used to mean mass, and the verb "to weigh" means "to determine the mass of" or "to have a mass of". Used in this sense, the proper SI unit is the kilogram (kg). </P> <P> In United States customary units, the pound can be either a unit of force or a unit of mass . Related units used in some distinct, separate subsystems of units include the poundal and the slug . The poundal is defined as the force necessary to accelerate an object of one - pound mass at 1 ft / s, and is equivalent to about 1 / 32.2 of a pound - force . The slug is defined as the amount of mass that accelerates at 1 ft / s when one pound - force is exerted on it, and is equivalent to about 32.2 pounds (mass). </P> <P> The kilogram - force is a non-SI unit of force, defined as the force exerted by a one kilogram mass in standard Earth gravity (equal to 9.80665 newtons exactly). The dyne is the cgs unit of force and is not a part of SI, while weights measured in the cgs unit of mass, the gram, remain a part of SI . </P> <P> The sensation of weight is caused by the force exerted by fluids in the vestibular system, a three - dimensional set of tubes in the inner ear . It is actually the sensation of g - force, regardless of whether this is due to being stationary in the presence of gravity, or, if the person is in motion, the result of any other forces acting on the body such as in the case of acceleration or deceleration of a lift, or centrifugal forces when turning sharply . </P>

If a quantity a has weight of 3 then the weight of a/3 will be