We know that the earth attracts every object with a certain force and this force depends on the mass (m) of the object and the acceleration due to the gravity (g). The weight of an object is the force with which it is attracted towards the earth.
We know that
F = m × a,
F = m × g.
The force of attraction of the earth on an object is known as the weight of the object. It is denoted by W. , we have
W = m × g
As the weight of an object is the force with which it is attracted towards the earth,
the SI unit of weight is the same as that of force, that is, newton (N). The weight is a force acting vertically downwards; it has both magnitude and direction. So it is vector quantity.
Weight is measured by Spring balance.
The value of g is constant at a given place. Therefore at a given place, the weight of an object is directly proportional to the mass, say m, of the object, that is, W ∝ m. It is due to this reason that at a given place, we can use the weight of an
object as a measure of its mass. The mass of an object remains the same everywhere, that is, on the earth and on any planet whereas its weight depends on its location because g depends on location.