Friction: Page 83

QUESTION: When would you want to create friction?

OBJECTIVE: Students will be able to name and give everyday examples of the four types of friction.

VOCABULARY: friction static friction sliding frictionrolling friction fluid friction

FrictionWrite these questions onto page 83

SKIP ONE LINE BETWEEN EACH QUESTION

1. Which direction does friction work?2. What two factors determine the amount of friction?3. What are the four different types of friction?4. Give two common examples of when friction isn’t bad.

What causes friction?Whenever two surfaces touch one another friction is created. Friction works opposite the motion of the object.

a baseball player sliding into 2nd base.

a ball rolling in the grass.

a surfboard against a wave

All of these everyday events are examples of friction.

What determines the amount of friction?Two factors can change the amount of friction.

1. how hard the surfaces are rubbing against one another

2. the type of surfaces

Example 1: The fast spinning tires of a racecar will create more friction than the tires on your family car.

Example 2: More friction will be created between a person sliding in dirt than sliding on water.

What are the four types of friction?Static Friction Sliding Friction

Rolling Friction

Fluid Friction

Static FrictionStatic friction is the most difficult to understand.

A goat standing on the side of a hill is being kept in place by the static friction between his hooves and the hill. If there wasn’t enough static friction, the goat would be pulled down the hill by gravity.

Sliding FrictionSliding friction can be seen hundreds of times a day.

If there wasn’t enough sliding friction between your gym shoe and the floor, you would slip all over the place.

Rolling FrictionRolling friction involves round objects.

Wheels are often put on heavy objects like refrigerators so they can be rolled around instead of dragged. Rolling friction is usually less than sliding friction.

The tires on a car provide friction to start and stop the car.

Fluid FrictionFluid friction is also very common.

Air and water are the two most common fluids. Solid objects are shaped in a way that allows them to slice through air and water rather than push through them.

Is Friction Always Bad?Friction causes two things to happen.

Friction causes heat. The more friction, the more heat. This isn’t usually good.

When the Space Shuttle returns to Earth the air causes enough friction to burn it up. .

Friction slows down athletes when they race. So they are always looking for ways to reduce friction.

Although friction causes moving objects to slow down, this isn’t always bad

If there was no friction you would not be able to stop your bicycle, your car or yourself.

Friction: page 83Check that the answers to these

questions are in your notes.

1. Which direction does friction work?2. What two factors determine the amount of friction?3. What are the four different types of friction?4. Give two common examples of when friction isn’t bad.

VOCABULARYFriction-the force created when two surfaces rub against each

other.

Static friction-a force that acts on two surfaces touching, but not moving.

Sliding friction-a force that acts when two solid surfaces slide past one another.

Rolling friction-a force that acts when one surface rolls against another surface.

Fluid friction-a force that acts when a solid moves through a liquid.