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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