GravityThe 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)

WeightWeight 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

MassThe measurement of the amount of matter “stuff” in an object

InertiaThe 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

ForceA push or a pull between objects

The Universal Law of GravitationThe force of gravity acts between all

objects in the universe. This means that all objects attract

each other!

Factors Affecting GravityMass – the greater the mass the greater the gravitational force

Distance – the smaller the distance, the greater the gravitational force

The Earth and youYou are attracted to the Earth and

the Earth is attracted to youYou pull on the Earth and the Earth

pulls on you… with the same amount of force!

FallingWhy 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 MoonYour mass will not change on the

moon Your weight will decrease since

there is less gravity on the moonThere is less gravity on the moon

because the moon is less massive than the Earth

Weight on other planetsGravity on the other planets

depends on the mass of the planet and the radius of the planet