Resistance is a force that slows the movement of one object over another. It can occur in liquids, such as water and in air. Air resistance is a type of friction between air and another material.

The terms weight and mass are often used incorrectly. Phrases like ‘a bag of sugar weighs 1 kg’ are not scientifically correct. This means that a 1 kg mass would be attracted to Earth by a force of 10 ...