Friction

Friction makes it possible:

To walkUse wheeled vehiclesSitHold books

Which is not something fiction helps you do?

A.) Float in outer space.

B.) Walk

C.) Sit in a seat.

D.) Hold things

Friction is a force that occurs when 2 surfaces oppose each other.

Friction is a force

A.) True

B.) False

Rub your hands together to produce friction.

Types of friction

StaticSlidingRollingFluid

Which is not a type of friction?

A.) Static

B.) Kinetic/Sliding

C.) Slippery

D.) Rolling

E.) Fluid

Which is not a kind of friction?

Static

Friction that acts on something that is not moving

Piano is held in place by static friction

Static friction keeps you in your seat

No heat or wear is generated

SlidingForce resulting when pushing or pulling an object over a surface.

Moving day—pushing a box across the floor

Heat and wear can result

Rolling

Contact is reduced because of rollers or wheels or ball bearings.

Skate boards have ball bearings in the wheels.

A cart has wheels. Less heat and wear will result.

Fluid friction

Resistance from a “liquid” or air.

Stirring a thick batterWalking through waterOlympic bike riders

The wheels on a car are an example of what type of friction?

A.) Static

B.) Sliding

C.) Rolling

D.) Fluid

A box sitting on a slope is an example of which type of friction?

A.) Static

B.) Rolling

C.) Fluid

D.) Sliding

Air resistance is what kind of friction?

A.) Static

B.) Sliding

C.) Rolling

D.) Fluid

Mu

is the coefficient of friction.

This depends on the two surfaces involved.

Typical values of Mu:

Wood on wood .25-.5(no units)

Glass on glass .9-1.0Steel on steel .6Steel on steel with oil .09Rubber on dry pavement 1.0Ski on snow .04Teflon on teflon .04

Which of the following is true about Mu?

A.) It is always the same number

B.) It is the "Coefficient of friction"

C.) It doesn't depend on the surfaces involved

Assignment:

Name 2 sports where friction is helpful and needed. Explain

Name 2 sports where friction is reduced for better performance. Explain

Reducing friction

A smooth surface does demonstrate as much friction as a rough surface.

A lubricant can be used to reduce friction.

You can get rid of friction by

A.) making the surfaces rougher

B.) using lubrication

C.) there is nothing you can do to reduce friction

Which of the following are true about friction?

A.) We couldn't live without it

B.) It depends on the two surfaces

C.) It can be a bad thing

D.) All of the above

E.) None of the above