ECP Chapter 4 PowerPoint

1. Essential College Physics
Chapter 4: Force and
Newton’s Laws of
Motion

2. Chapter 4 Objectives
• Understand force and mass
• Describe Newton’s three laws of motion
• Analyze the forces in a problem and draw an
appropriate force diagram
• Relate the net force to changes in motion
• Describe the effects of friction and drag
forces
• Recognize the role of forces in circular
motion

3. Forces (66)
• Contact forces
• Force at a distance
• Tactic 4.1 (67)

4. Net Force (67)

5. Free Body Diagram (67)

6. Newton’s First Law (68)
• Mass and inertia (The law of inertia)
• “A body at rest tends to stay at rest and a
body in motion tends to stay in motion at a
constant velocity unless acted upon by an
unbalanced, external force.”
• “If the net force on an object is zero, then the
object maintains constant velocity.”

7. Newton’s Second Law (69)
netF m a 
Net force, N
Mass, kg
Acceleration, m/s2

8. Weight (70)
• The force exerted by the earth’s gravitational
pull
• The acceleration due to gravity: g=9.8 m/s2
• SI system versus the English system
w m g Weight, N
Mass, kg
Acceleration due to
gravity, 9.8 m/s2

9. Frames of Reference (71)

10. Newton’s Third Law (71)
• “To every action there is an equal and
opposite reaction.”
• “When two objects interact, the force that
object A exerts on object B is equal in
magnitude and opposite in direction to the
force that B exerts on A.”
• Rocket thrust (71)
AB BAF F 

11. Newton’s Laws Problems
• Conceptual Example 4.2 (72)
• Example 4.3 (72)
• Conceptual Example 4.4 (73)

12. Problem Solving (75)

13. Normal Force (75)

14. The Normal Force (75)

15. More Problems
• Example 4.6 (78)
• Example 4.7 (78)

16. Atwood Machine Lab
• Purpose: To predict the acceleration of a two
body system
• Motion detector (protect it!)
• Close to equal masses
• Calculate per cent error

17. Friction (79)
• Relevant factors
• Static friction, kinetic friction, rolling friction,
drag
f n Frictional
force, N
Coefficient of
friction (no units)
Normal force, N

18. Friction (80)

19. Friction Problems (80)
• Example 4.8 (80)
• Example 4.9 (81)
• Example 4.10 (82)

20. Centripetal Force (84)
• String, rope, chain, or gravity
2
r
mv
F
R

2
r 2
4 mR
F
T


Centripetal
Force, N
Mass, kg
Mass, kg
Velocity, m/s
Radius, m
Period, s

21. Centripetal Force Problems
• Example 4.11 (84)
• Example 4.12 (85)
• Example 4.13 (85)

22. Chapter 4 Problem Sets
• Honors: P. 88, Ex. 30, 42, 44, 48, 50, 60, 62,
64, 66, 68, 74, 84, 94, 112
• UConn: P. 88, Ex. 30, 42, 44, 48, 50, 56, 58, 60,
62, 64, 66, 68, 74, 84, 94, 102, 112, 114