MOTION & FORCE

Balanced and Unbalanced Forces action exerted on a body in order to change body’s state of rest or motion. has magnitude and direction. NET FORCE combination of all forces acting on an object. BALANCED FORCES Objects either do not move or move at constant velocity. UNBALANCED FORCE any change in an object’s state of motion or rest.

FRICTION force that opposes motion between two surfaces that are in contact. opposes applied force.

STATIC FRICTION resists initiation of sliding motion between two surfaces that are in contact and at rest. is greater than kinetic friction. Object not moving

KINETIC FRICTION opposes movement of two surfaces that are in contact and are sliding over each other. Object is moving

TYPES OF KINETIC FRICTION

SLIDING FRICTION When objects slide past each other

FLUID FRICTION When an object moves through a fluid (air, water…) and surface of object

ROLLING FRICTION When a round object rolls over a flat surface

FRICTION AND MOTION Friction can be helpful or harmful. necessary to roll a vehicle or hold an object. can also cause excessive heating or wear of moving parts.

HARMFUL FRICTION CAN BE REDUCED Lubricants Smooth surfaces Replace with another type friction

HELPFUL FRICTION CAN BE INCREASED. Make surfaces rougher Increase forces pushing together