FORCES

FOUNDATIONS OF PHYSICS

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

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

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

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

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.