Gravity and Inertia

Gravity The force that pulls objects towards each other – a force of attraction between objects! On Earth, gravity is pulling everything straight down toward the center of the Earth (of course we get stopped by the ground)

Weight Weight is the force of gravity on a person or object on the surface of a planet Weight depends on mass and the force of gravity at a specific location

Mass The measurement of the amount of matter “stuff” in an object

Inertia The tendency of an object to resist a change in its motion Mass changes an object’s inertia – the more mass the more inertia… the object will be harder to start or stop

Force A push or a pull between objects

The Universal Law of Gravitation The force of gravity acts between all objects in the universe. This means that all objects attract each other!

Factors Affecting Gravity Mass – the greater the mass the greater the gravitational force Distance – the smaller the distance, the greater the gravitational force

with the same amount of force! The Earth and you You are attracted to the Earth and the Earth is attracted to you You pull on the Earth and the Earth pulls on you… with the same amount of force!

Falling Why when we fall are we pulled down towards the Earth instead of pulling the Earth up towards us? The Earth has a whole lot more mass (more inertia) – needs more force to move!

Why are we pulled more towards the Earth than the moon? The Earth has more mass and is closer to us!

Mass and Weight on the Moon Your mass will not change on the moon Your weight will decrease since there is less gravity on the moon There is less gravity on the moon because the moon is less massive than the Earth

Weight on other planets Gravity on the other planets depends on the mass of the planet and the radius of the planet