1. Physics A First Course
Energy and Systems
Chapter 5

2. Energy and Systems Forces in Equilibrium
5.1 The Force Vector
5.2 Forces and Equilibrium
5.3 Friction
5.4 Torque and Rotational Equilibrium

3. 5A Investigation: Equilibrium and Forces
Key Question:
What can we say about forces when nothing is moving?
*Students read text section 5.1
AFTER Investigation 5A

4. 5A Investigation Topics
Use spring scales.
Make an object in equilibrium.
Measure forces on an object that is in equilibrium.
Draw free-body diagrams.
Measure the force of gravity.
Distinguish between weight and mass.

5. Chapter 5.1 Objectives and Vocabulary
Draw vectors to scale to represent a quantity's magnitude and direction.
Solve vector problems.
Find a vector's components.
scalar
magnitude
vector
component
free-body diagram

7. 5.1 Pythagorean Theory
side b
side a
a2 + b2 = c2
hypotenuse, side c

8. Chapter 5.2 Objectives and Vocabulary
Explain what it means to say an object is in equilibrium.
Use free-body diagrams to find unknown forces.
Explain how springs exert forces.
Add force vectors.
equilibrium
normal force
resultant
Hooke's lab
spring constant

11. 5B Investigation: Friction
Key Question:
How do we account for friction?
*Students read text section 5.3
AFTER Investigation 5B

12. 5B Investigation Topics
Measure kinetic energy of a system.
Determine the force of friction from experimental data.
Compare friction in a car to friction in a sled.
Use Newton's second law to calculate force of friction in a rolling car.
Compare the strength of sliding friction to that of rolling friction.
Determine how the force of friction varies with speed.

13. Chapter 5.3 Objectives and Vocabulary
Distinguish between sliding and static friction.
Explain the cause of friction.
Discuss reasons to increase or decrease friction.
friction
sliding friction
static friction
lubricant

15. Chapter 5.4 Objectives and Vocabulary
Explain how torque is created.
Calculate the torque on an object.
Define rotational equilibrium.
torque
rotate
axis of rotation
line of action
lever arm
rotational equilibrium