1. Chapter 5-3 The Foundations of Physical Science
FORCES
Chapter 5-3
The Foundations of Physical Science

2. Forces and Equilibrium
We almost never feel only one force,
Net Force is the sum of ALL forces acting on an object
The word NET means TOTAL
NET FORCE also means that the direction of each force is considered when multiple forces are added

3. AIRPLANES
For airplane to fly at a constant speed on a level path, the forces must all balance
Balanced forces result in a net force of zero
An airplane has 4 forces acting upon it
Weight
Drag (air friction)
Thrust (of engines)
Lift (flow of air over wings)

5. Equilibrium
Equilibrium is the state in which the net force on an object is zero
Equilibrium does NOT mean there are no forces!
Equilibrium means all forces cancel each other out leaving a net force of zero.

7. Equilibrium and Normal Forces
A normal force is created whenever an object is in contact with a surface.
The normal force has equal strength to the force pressing the object into the surface, which is often the object’s weight.
The normal force is sometimes called the support force.

8. Force Diagram
How can you keep track of many forces with different directions?
A force diagram is the answer!
A force diagram is a diagram showing all the forces acting on an object.

9. Force Diagram
It only contains only a single item (like a book or table)
All connections and supports are taken away and replaced by the forces they exert on the object
AN ACCURATE DIAGRAM INCLUDES EVERY FORCE ACTING ONAN OBJECT INCLUDING WEIGHT, FRICTION, AND NORMAL FORCES