Physics Weight and Mass
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Physics
Weight and Mass
What is the difference between weight and mass?
Mass is the amount of matter in a solid object, or a volume of a gas or liquid.
Weight is the force of gravity acting on a mass.
If you were to move an object, for example a lump of cheese, from the Earth to the Moon, its mass would not change, but it will weigh less. This is because the amount of matter in the cheese stays the same, but the gravitational force acting on the cheese by the Moon would be less than the gravitational force acting on the cheese on Earth.
Weight should be measured in Newtons and has a direction component (vector). This direction is normally downward due to gravity, a force between two objects that depends on the mass of the objects and the distance between them. (The Earth has much larger mass than the Moon). A component of weight can also be sideways, such as the force of a car hitting a wall.
Mass is usually measured in kilograms.
The above is a scientific definition. In day-to-day life. most people use the term “weight” when measuring the mass of objects, such as a human body or a piece of cheese. This is because gravity is almost constant (within 1%) at the surface of the Earth (average 9.78 m/s2at the Equator).
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