This chapter discusses forces in two dimensions, including friction. It introduces kinetic and static friction, explaining that kinetic friction opposes motion between two surfaces in contact, while static friction prevents motion. The chapter also discusses inclined planes and equilibrium, defining an equilibrant as the force needed to balance other forces and cause equilibrium. Key concepts are that friction proportional to the force pressing surfaces together, and that the equilibrant is a force equal in magnitude but opposite in direction to the net force on an object.

1. Chapter 5: Forces
in Two Dimensions

2. Chapter Overview
This chapter extends the discussion of Newton’s laws in the previous
chapter to two dimensions. The second section introduces kinetic and static
friction and illustrates how to include friction in Newtonian analyses.
Finally, additional two-dimensional situations are discussed including
inclined planes as is the concept of an equilibrant.

3. What You’ll Learn
1. You will use Newton’s laws to analyze motion when friction is
involved.
2. You will use Newton’s laws and your knowledge of vectors to analyze
motion in two dimensions.

4. Section 5.2: Friction
Monday, October 23, 2023

5. Objectives
● Define the friction force.
● Distinguish between static and kinetic friction.

6. Vocabulary
● Kinetic friction
● Static friction

7. Static and Kinetic Friction
● There are two types of friction.
○ Both oppose motion
● Kinetic friction is exerted on one surface by another when the two
surfaces rub against each other because one or both of them are
moving.
● Static friction is the force exerted on one surface by another when
there is no motion between two surfaces.

8. Key Concepts
● A frictional force acts when two surfaces touch
● The frictional force is proportional to the force pushing the
surfaces together.

9. Section Review and Mastering Homework
Review #27 and 31
Mastering homework: Pg 140 #57

10. Section 5.3: Force and
Motion in Two Dimensions
Wednesday, October 25, 2023

11. Objectives
● Determine the force that produces equilibrium when three forces
act on an object.
● Analyze the motion of an object on an inclined plane with and
without friction.

12. Vocabulary
● Equilibrant

13. Equilibrium Revisited
● When the net force on an object is zero, the object is in
equilibrium
● The object will not accelerate because there is no net force acting
on it; an object in equilibrium is motionless or moves with a
constant velocity.
● Equilibrium can occur no matter how many forces act on an object
● A force that puts an object into equilibrium is called the
equilibrant.

14. Key Concepts
● The force that must be exerted on an object to cause it to be in
equilibrium is called the equilibrant.
● The equilibrant is found by finding the net force on an object, then
applying a force with the same magnitude but opposite direction.

15. Mastering Concepts
Page 140 #61 & 62