Newton’s First Law - GCSE Physics Definition

Newton’s First Law, also known as the law of inertia, states that an object will stay at rest or keep moving at the same speed in a straight line unless a force acts on it. This means that if nothing pushes or pulls on an object, it will not change how fast it is going or the direction it is moving. For example, a ball lying on a flat surface will not roll away unless someone kicks it, and a car driving in a straight line will keep moving in that direction unless the driver steers it differently or brakes. This law helps us understand how and why objects start and stop moving.