2 Friction DefinitionFriction 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!share.ehs.uen.org
3 Factors that Affect Friction How hard the surfaces push against each other – the more force, the higher the frictionThe type of surfaces involved – the smoother the surface, the lower the friction
4 Friction and Smooth Surfaces Even apparently smooth surfaces actually have microscopic irregularities and bumps. When these come in contact with another surface friction occurs.
5 Direction of FrictionFriction acts in the opposite direction of motion, so if the object moves towards the right the frictional force will be towards the left.
6 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.
7 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 movingeducation-portal.com
8 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
9 Usefulness of Sliding Friction It can keep you from slipping, sliding and falling (example: sand on an icy road)!
10 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.
11 Rolling Friction and Engineers Engineers use ball bearings to reduce friction – the ball bearings roll between moving parts.news.thomasnet.com
12 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
13 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.