What are the differences between mass, weight, force and load?

Find out when you should use these terms

We use these words on a daily basis, but do you really know the difference?  

• Mass

  Mass is a measure of the amount of material in an object, directly related to the number and type of atoms present in the object. Mass does not change with a body's position, movement or alteration of its shape unless material is added or removed. The unit of mass in the SI system is the kilogram (kg).

• Weight

  In the trading of goods, weight is taken to mean the same as mass and is measured in kilograms. Scientifically, however, it is normal to state that the weight of a body is the gravitational force acting on it and hence it should be measured in newtons (N), and that this force depends on the local force due to gravity. To add to the confusion, a weight is an artefact of calibrated mass normally made from a dense metal. So, unfortunately, weight has three meanings and care should always be taken to appreciate which one is meant in a particular context.

• Force

  Force is a measure of the interaction between bodies. It takes a number of forms including short-range atomic forces, electromagnetic and gravitational forces. Force is known as a vector quantity, as it has both direction and magnitude.

• Load

  Load is a term frequently used in engineering to mean the force exerted on a surface or body.

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