Newton's Laws of Motion

In the late 1600s, a scientist named Isaac Newton figured out three important rules about motion. These rules explain why objects move, stop, and change direction. Newton's three laws of motion help us understand everything from throwing a ball to launching a rocket.

The First Two Laws

Newton's first law says an object at rest stays at rest, and a moving object keeps moving, unless a force acts on it. This is why you need a seatbelt. If a car stops suddenly, your body wants to keep moving forward. Newton's second law says heavier objects need more force to move. Pushing a bowling ball is harder than pushing a tennis ball.

The Third Law

Newton's third law says that for every action, there is an equal and opposite reaction. When you push against a wall, the wall pushes back against you. When a rocket shoots hot gas downward, the gas pushes the rocket upward. When you jump, your feet push down on the ground and the ground pushes you up.

Fun Facts

• Legend says Newton started thinking about gravity when an apple fell on his head, but this is probably not exactly true.
• Newton published his three laws of motion in 1687 in a famous book called the Principia.
• Astronauts in space demonstrate Newton's first law. Objects float because there is no friction to slow them down.

Did You Know?

Newton's laws are so accurate that NASA still uses them to calculate the paths of spacecraft today. These 300-year-old rules are good enough to send rockets to other planets!