Newton’s Laws of Motion

Galileo’s Inertia After watching Jupiter’s Moons Galileo became convinced that objects had a tendency to keep whatever state of motion they had. He called this the objects’ inertia He confirmed it by doing experiments using balls rolling up and down ramps.

Isaac Newton (1642-1727) Inspired by Galileo and Kepler, before he was 23 Isaac Newton laid the foundation of modern physics. Galileo inspired him to create His three laws of motion Kepler inspired his Universal Law of Gravity Newton would go on to: make discoveries in Optics and to lead efforts to find an astronomical solution to the problem of longitude by using Jupiter’s moons The first Physics, was Astrophysics.

Changes in Motion There are two ways that an object can change its motion: 1. It can change its speed. Speed up, slow down, stop or start 2. It can change direction A change in motion is called an acceleration. Notice that an object orbiting in a circle or ellipse is changing direction and therefore accelerating.

The First Law` Isaac Newton developed the idea of inertia into his First Law of Motion “An object in motion stays in motion in a straight line, one at rest stays at rest, unless a force acts on it.”

The Second Law The Second Law states that to change an object’s motion you must push or pull on it with a force. The amount Net force (F) is directly related to… the inertia of the object (mass, m) and how much change of motion (acceleration, a) you want to make . F = m a Remember: an acceleration can be a change in the object’s speed or in its… Direction.

The Third Law “For Every action there is an equal and opposite reaction” Is Newton’s Third Law of motion…simplified. It means that if Object “A” exerts a force on object “B” then “B” must push right back on “A” with the same amount of force in the opposite direction!

The 3rd law and Spaceships All rockets, and most spaceship designs rely on Newton’s 3rd law to move. Their engines produce exhaust that is pushed out of the rocket, Action: Rocket pushes exhaust back Reaction; Exhaust pushes the rocket forward That’s how rocket can work in space where there is nothing to push off of.