Newton's first law: inertia and equilibrium

Newton's first law says an object at rest stays at rest, and an object in motion keeps moving at the same speed in a straight line, unless a net external force acts on it. Inertia is this tendency to resist changes in motion, and it depends on mass: a loaded truck is much harder to start or stop than a bicycle. When all the forces on an object balance, so the net force is zero, the object is in equilibrium and its velocity does not change, whether it is sitting still or cruising at constant velocity. Seat belts and airbags work because of inertia: when a car stops suddenly, your body keeps moving forward until a force stops it. A space probe far from any planet keeps coasting without firing its engines for the same reason.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report