According to Newton's second law
of motion (F = ma), the mass of a body can be determined by measuring the
acceleration produced in it by a
constant force. (i.e) m = F/a.
Intertial mass of a body is a measure
of the ability of a body to oppose the
production of acceleration in it by an external force.
If a constant force acts on two
masses mA and mB and produces accelerations
aA and aB respectively, then, F = mAaA
mA/ mB = aA
The ratio of
two masses is independent of the constant force. If the same force is applied
on two different bodies, the inertial mass of the body is more in which the
acceleration produced is less.
If one of the two masses is a
standard kilogram, the unknown mass can be determined by comparing their
Newton's law of gravitation, the gravitational force on a body is proportional
to its mass. We can measure the mass of a body by measuring the gravitational
force exerted on it by a massive body like Earth. Gravitational mass is the mass of a body which determines the magnitude of gravitational pull between the
body and the Earth. This is determined
with the help of a beam balance.
If FA and FB
are the gravitational forces of attraction on the two bodies of masses mA and mB due to the Earth, then
FA = GmAM /R2
FB = GmBM /R2
where M is mass of the Earth, R
is the radius of the Earth and G is the gravitational constant.
mA/ mB = FA
If one of the two masses is a standard kilogram, the unknown mass can be determined by comparing the gravitational forces.