Motion, forces and energy

Units of measurement are are used to represent physical quantities like length, weight and other values. Units can be imperial or metric and can be converted by conversion factors.

The movement of objects can be described using motion graphs and numerical values. These are both used to help in the design of faster and more efficient vehicles.

Mass is a measure of the quantity of matter in an object at rest relative to the observer. Weight is a gravitational force on an object that has mass.

Density describes how closely packed the particles are in a solid, liquid or gas. Matter is made up of small particles called atoms. Atoms can exist on their own or as molecules.

Forces are responsible for changing the motion of objects. If more than one force is present, the shape of an object can also be changed.

Momentum can be thought of as a combination of mass and velocity. Momentum helps explain some of the most important interactions in nature.

Energy is a key principle in physics. The rate at which energy is transferred is called power, the amount of energy that is transferred is called efficiency.

Every living thing on Earth is in balance with the pressure of the air or water around it. Pressure helps blood to move around the body and allows organisms to breathe.

Learn all about forces for your IGCSE physics exams, with scientists James Stewart and Ellie Hurer.

Learn all about energy for your IGCSE physics exam with this podcast.