# Newton's Laws of Motion

## Newton's First Law of Motion

Newton’s first law of motion states that every object persists its own state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it. In simpler terms, an object in motion will stay in motion and an object at rest will stay at rest unless acted on by an outside force. This law is also called the law of inertia. This means that if nothing is happening to you, nothing ever will happen unless something changes. If you are moving, you would walk in that direction forever unless something stops you.

A real life example of this law is passengers in a car. If you are driving and wearing your seatbelt, you accelerate and decelerate with the car. So, if you car hits a wall inertia would want you to fly out, but your seatbelt stops you. When the car hits the wall and its motion stops and you were not wearing a seatbelt, you would keep accelerating forward because there is nothing to stop you from the inertia.

This picture shows someone kicking a ball. This ball was originally not in motion. It would've stayed like that. But, a force acted on it. That force was the boy kicking it. Now, the ball will roll unless acted on by another force that stops it.

## Newton's Second Law of Motion

Newton's second law of motion states that force is equal to the change in momentum per change in time. For a constant mass, force equals mass times acceleration or force = mass * acceleration. For example, a mass of a box is 10 kg and its accelerates at 8 m/s/s. To figure out the force that was put on the object, you would multiply the mass by the acceleration, 10 kg * 8 m/s/s, and get the force. In this situation, the force would by 80 N.

A real life example of this law can be moving an object. Let's say that you are pushing a 10 pound box and a 1 pound box with the same force. The acceleration will be different because one box is lighter and the force is not as strong on it. So, the difference in acceleration depends on the difference in the masses.

This picture shows 2 boys pulling different sized rocks. They boy who is pulling the heavier rock is putting force into it and it is not going to have the same acceleration as the other boys rock. The other boy with the smaller rock is also putting force into pulling the rock. His rock will go at a faster acceleration than the heavier rock.

## Newton's Third Law of Motion

Newton's third law of motion states that for every action, there is an equal and opposite reaction. It can also be stated as for every force, there is an equal and opposite force. This means that forced are found in pairs. For every force, there is another force that acts on that force in an opposite direction.

A real life example of this law is when you sit in a chair. Your body goes downward and land on the chair. The chair creates a force upward. If the chair didn't create this force, the chair would collapse.

In this picture, a man is pushing against a brick wall. He puts force on the wall and the wall pushes force towards him. This way, the wall won't fall on him and he won't push the wall over. It is balanced.

## Vocab

Inertia - the tendancy of an object to resist motion

Mass - the amount of matter in an object

Force - a push or pull

Acceleration - an increase in the rate or speed of something