# Lesson 2- Changes in Motion

## Gravity

Description: gravity is a force that pulls objects down. This force brings objects back to the earth. This force also keeps the planets in orbit with the sun. Examples:-a pencil rolls off a table and falls to the ground- you drop a book and it slams on the floor

## Weightlessness

WeightlessnessÂ is when you are thinking you have no weight. Many times you are floating around when you are in weightlessness. Even though you think you have no weight you keep your same weight. Some examples are when you are in outer space you will be floating around unless you have gravity acting upon you. Also if you are skydiving you feel as if you have no weight.

## Momentum

Momentum is when the speed and mass of an object are added together. This is useful for studing the motion of objects colliding. A soccer ball has more momentum than a ping-pong ball traveling at the same speed. This is because the soccer ball has more mass within it. Another example is a bowling ball rolling on the floor would have more momentum than a golf ball.

## Newtons 2 Law

This says that the acceleration depends on the amount of net force applied to it. Hitting a home run depends on how hard you swing. The amount of force applied to a golf ball needs to be just enough to get it to the hole.

## Newtons 3 law

For every action force there is an equal and opposite reaction force thats what this law is about. A diver pushes down on the board but it pushes her back up so she can dive. A pitcher throws the ball and the batters bat pushes back to hit the ball.