# Chpt. 11 Lesson 2 Science Concepts

## Newtons First Law of Motion

Newtons First Law of Motion states that an object at rest tends to stay at rest and an object in motion tends to stay in motion unless an unbalanced net force acts upon it. This means that when an object is still it will remain still, and when an object is moving it will stay moving unless someone applies a force to it.    For example, when you set a glass on the counter it will still be there in an hour unless someone has moved it.

## Newtons Second Law of Motion

Newtons Second Law of Motion states that acceleration depends on the objects mass and the amount of net force applied to it. This means the heavier the object is, the harder it will be  to carry, move, or hold.     For example, a desk with nothing in it will be able to be lifted faster and more efficient than a desk thats full of things.

## Newtons Third Law of Motion

Newtons Third Law of Motion states that for every action force there is an equal and opposite reaction force. This means that when you apply a force to something there will be an opposing force.    For example you roll a baseball down a street the street exerts a force back on the baseball. In this case, the opposing force is friction.

## Weightlessness

Weightlessness is when an object has or feels no detectable weight. It is kind of like the feeling when you are at the top of the rollercoaster of when you are lifting off in an airplane.

## Mass and Weight

Mass and weight are not the same thing. Mass is how much much matter there is in and object.Weight is how much gravitational pull there is on the object. Mass is, for example, how big the object is. Weight is how heavy an object is.  Weight uses a scale to measure.

## Gravity

Gravity is a type of force. It is a force that pulls you back down to Earth. Gravitational pull is stronger to objects that are closer together than to objects that are farther apart. If you throw a ball in the air on Earth it will eventually come back down. If you throw a ball up on the moon it will never come back. That is because there is no gravitational pull on the moon.