1.3 Mass and weight
Mass:
Mass is a measure of the quantity of matter in an object at rest. (Mass is the amount of matter in an object)
Weight:
Weight is the force of gravity acting on an object that has mass. (Weight is a gravitational force)
W = mg
W = Weight (in Newtons)
m = Mass (Kg)
g = Gravity (on earth 9.8m/s^2)
The SI unit of weight is the same as that of force: the newton (N)
One newton is equal to 1 kilogram meter per second squared.
$$One\;newton(1N)\;=\;Kgms^{-2}$$
Gravitational field strength
Gravitational field strength Defined as force per unit mass;
$$g={{W}\over{m}}$$
W = Weight (in Newtons)
m = Mass (Kg)
g = Gravity (on earth 9.8m/s^2)
Mass Vs. Weight
| Mass | Weight |
| Mass always remains the same | Weight can change with location. |
| Mass is measured in Kilograms, Grams etc. | Weight is measured in Newtons (N) |
| Mass can never be zero | Weight can be zero |
| Mass has only magnitude (Scalar) | Weight has both magnitude and direction (Vector) |
| Mass may be measured using an ordinary balance | Weight is measured using a spring balance. |
The Greater the mass of a body, the greater is the inertia or resistance to change of motion
The weight of an object and its mass are directly proportional. For a given gravitational field strength, the greater the mass of the object, the greater its weight.