1. FORCES FOUNDATIONS OF PHYSICS

2. FORCE Interaction between objects Usually a push or a pull Classified as either contact forces or field forces Contact Forces Interactions that occur when the objects are in direct contact with each other Examples: Force of kick, Friction, etc. Field Forces Interactions that occur over a distance due to some type of field. Thus, the objects do not have to be in direct contact. Examples: Gravity and Electromagnetic Force

3. FRICTION Contact force that results from the particles of the two objects surfaces sticking together. Always opposes motion (in the opposite direction of the motion of the object) Always parallel to surface Two types of friction: Kinetic Friction and Static Friction Static Friction is always greater than Kinetic Friction

4. NORMAL FORCE Contact pushing force between objects Always perpendicular to the surfaces in contact TENSION Contact pulling force between objects Can act along a rope, string, cable, etc

5. LIFT Force of air particles colliding with surface of the object Like friction, drag opposes motion Drag increases as the speed of the object increases One of the four forces associated with flight DRAG Contact force resulting from increased air pressure under the object pushing upward (usually) on the object One of the four forces associated with flight

6. GRAVITY Forward pushing force due to an engine, motor, or some other type of technology One of the four forces associated with flight THRUST Attractive (pulling) field force between objects. Depends on the mass of the objects and how far apart they are On Earth, the force of gravity is called weight.