2. What is a Force? the influence that produces a change in a physical quantity; "force equals mass times acceleration"

3. Friction and Tension
Weight and Normal force

4. Weight, Friction, and Boyancy force

5. Normal Force
When a body presses against a surface, the surface pushes back on the body with a force that is perpendicular to the surface.
The normal force always self-adjusts to equal the force pressing the body to the surface.

6. Tension
Tension is a force transmitted by a rope, cord, cable or the like which transmits a force, undiminished, from one end to an object attached at the other end, it always pulls.

7. Tension The tension force pulls on a body.
The cord is often assumed to be massless.
We usually assume pulleys to be frictionless
A string has a single tension force (magnitude) on both sides of a frictionless pulley.

8. Weight, (Gravitational Force)

9. Friction

10. A book whose mass is 2 kg rests on a table
A book whose mass is 2 kg rests on a table. Find the magnitude of the force exerted by the table on the book. FN Fg
Note: This force is called the Normal force because it acts perpendicular to the contact surface of the object.