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FRICTION
FRICTION DEFINITION Friction occurs when 2
objects are in contact with each other. The objects apply or exert a force on one another during this time.
Friction acts in the opposite direction of motion – so it is the force that resists movement!
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FACTORS THAT AFFECT FRICTION
How hard the surfaces push against each other – the more force, the higher the friction
The type of surfaces involved – the smoother the surface, the lower the friction
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FRICTION AND SMOOTH SURFACES
Even apparently smooth surfaces actually have microscopic irregularities and bumps. When these come in contact with another surface friction occurs.
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DIRECTION OF FRICTION
Friction acts in the opposite direction of motion, so if the object moves towards the right the frictional force will be towards the left.
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STATIC FRICTION
Definition: The friction that occurs when
objects are not moving. It is the friction that keeps objects in place.
Example: A box sitting on the ground, your
books sitting on a table, your backside against the chair.
HOW TO “OVERCOME” STATIC FRICTION The force needed to
start an object moving must be greater than the static friction.
Reason why a greater force is needed to start an object moving than to continue it moving education-portal.com
SLIDING FRICTION
Definition: The friction that occurs when 2 solid objects move against each other (or 1 object moves over another)
Example: Bicycle brakes, skinning your knee, walking, writing
USEFULNESS OF SLIDING FRICTION
It can keep you from slipping, sliding and falling (example: sand on an icy road)!
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ROLLING FRICTION
Definition: The friction that occurs when an object
rolls across a surface. Easier to overcome than sliding friction.Example: Anything with wheels (cars,
skateboards) or a ball rolling.
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ROLLING FRICTION AND ENGINEERS
Engineers use ball bearings to reduce friction – the ball bearings roll between moving parts.
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FLUID FRICTION
Definition: The friction that occurs when a solid
objects moves through a fluid. A fluid is a gas or liquid – they flow easily!
Easier to overcome than sliding friction.
Example: Anything moving through the air or
water: riding a bike, surfing, swimming, sky diving
USEFULNESS OF FLUID FRICTION
Parts of machines move more easily when they are oiled.
Fluid friction is what slows down a skydiver when the parachute is opened.
