Why things move the way they do
Isaac Newton’s three laws of motion, published in 1687, are still the foundation for almost everything we know about how objects move — from a dropped pencil to a rocket launch.
First Law: Objects like to keep doing what they’re already doing
An object at rest stays at rest, and an object in motion stays in motion at a constant speed and direction, unless a force acts on it. This is also called the law of inertia. A hockey puck sliding on frictionless ice would never stop — it’s friction and air resistance, not some “natural tendency to slow down,” that brings it to a halt.
Second Law: Force equals mass times acceleration
F = ma
The harder you push something (more force), the faster it speeds up (more acceleration) — but heavier objects (more mass) are harder to accelerate. This one equation explains why it’s easier to push an empty shopping cart than a full one.
Third Law: Every action has an equal and opposite reaction
When you push on something, it pushes back on you just as hard. This is why rockets work: the engine pushes exhaust gas backward, and the gas pushes the rocket forward with equal force.
Try this
Sit on a rolling chair and throw a heavy backpack away from you. You’ll roll backward — that’s Newton’s third law in action.