WEIGHT, MASS, AND THE FORCE OF GRAVITYUnit 5 Lesson 1

Unit overview• In this unit you will be learning about forces and motion.• A force is a push or pull exerted on an object.

Remember Mass?• In Unit 3 you learned that mass is the amount of matter in

an object.• The quantity (amount) of matter in an object does not

change.• An object’s mass is constant (does not change).• The mass of an object will stay the same regardless of

how much gravity acts on the object.

Mass and Weight are not the Same Thing

• Weight is the gravitational force exerted on an object.• Weight varies depending on how much gravity acts on an

object.

Let’s compare mass and weight• An object will have the same mass (amount of ) on the

moon as it does on Earth.• The object’s weight will be different because gravity is

different.• Objects on the moon weigh about 1/6th of what they weigh

on earth.

Would you rather weigh yourself on top of a mountain or at sea level?• On top of Mt. Everest, you would weigh slightly less than

you would at sea level.

Gravitational Force• Gravity is the force of attraction between two objects.• Gravity depends on the masses of the objects and the

distance between the objects.

Gravity on Earth• The gravity on Earth is obvious because it is the force that

keeps us on the surface of Earth.

Gravity on the Moon• Gravity is also the force that keeps the moon in orbit

around the earth.

Gravity is a Force• Gravity is a force, but gravity does not touch an object

when it acts on it.• Gravity pulls an object and affects the object’s weight.