1. Unit 2 Force & Motion
Ch 5 Sec 3
Friction

2. Friction
friction - force that resists sliding between two touching surfaces
slows down/stops moving objects
w/o friction, a moving object would continue to move in a straight line at a constant speed

3. 3 Types of Friction static friction sliding friction rolling friction
prevents an object at rest from moving - caused by the attraction of atoms on touching surfaces - rougher, heavier objects have more static friction
slows down a sliding object - caused by the microscopic roughness of surfaces
makes a rolling object continue to roll

4. Air Resistance
air resistance - a form of friction that slows down objects moving through air (lighter, broader objects have more air resistance)

5. Changing Friction Reducing Friction Increasing Friction Use lubricants
Smoothing with Sand Paper
Ball Bearings
Sand on Ice
Press Harder (more force)