Friction and Gravity

What is friction? The force that two surfaces exert on each other when they rub against each other Time to...brainstorm! What are some examples of friction?

Friction The strength of the force of friction depends on 2 factors: How hard the surfaces push together The types of surfaces involved Friction acts in a direction opposite to the direction of the objects in motion

Which has more friction? >

4 Types of friction Static Friction: friction that acts on objects that are not moving. Must overcome static friction for an object to start moving. Sliding Friction: occurs when two solid surfaces slide over each other. Can be useful, i.e. brakes and types of shoes. Rolling Friction: when an object rolls across a surface. Fluid Friction: occurs when a solid object moves through a fluid. For example, surfing, boating, etc.

Friction Activity Fill the bowl halfway with water Put the smooth ball in the water and spin it Do the same thing with the tennis ball Which ball spins faster? Why?

Gravity a force that pulls objects toward each other The Law of Universal Gravitation: the force of gravity acts between all objects in the universe

School house rocks- gravity

Bill Nye: gravity

What affects gravity? MASS and DISTANCE Mass: the measure of the amount of matter in an object If the mass increases, the force of gravity increases If distances increases, the force of gravity decreases

Why does that happen?

hammer and feather drop on moon

What happens if there is no gravity??