# Newton’s Laws of Motion

Every now and again, someone comes along who thinks outside the box and changes the way we understand our world. Sir Isaac Newton was one of those people.

## Sir Isaac Newton

Isaac Newton was born in 1642 in England. He worked as a mathematics professor at the University of Cambridge, but he also studied and wrote about physics and astronomy.

In 1687, Newton published Mathematical Principles of Natural Philosophy. This book explained the three laws of motion.

Let’s take a look at the laws that Newton uncovered!

## The Law of Inertia

The Law of Inertia says that an object in motion will stay in motion unless some outside force acts on it.

If you threw a ball in outer space and it never hit anything, it would keep going at the same speed and in the same direction – forever. This is the Law of Inertia.

On Earth, gravity is an outside force that changes the inertia of a ball. When you throw a ball on Earth, gravity pulls the ball back to the ground.

## The Law of Force

The Law of Force describes how to calculate force. Force is equal to the mass of an object times the acceleration of the object. Acceleration is the rate at which something changes speed.

The more mass an object has, the more force you have to apply to get it to accelerate. It’s easy to get a pebble started rolling down a hill, but it takes more force to push a big rock.

## The Law of Conservation of Momentum

Newton’s third law of motion states that for every action there is an equal and opposite reaction. Forces occur in pairs that are identical and opposite.

Newton’s third law is easier to understand when you think about swimming. Your hands and feet move the water as you swim. The water pushes back with equal and opposite force. The force of the water moves you across the pool!

Written by Laura McCamy

Edited by Gabriel Buckley, MS Professional Natural Sciences