1. Chapter 4 Objectives:
1) Define FORCE; including units.
2) Identify the three types of forces providing examples of each.
3) Be able to draw “free-body” diagrams for a set of forces acting on a body.
4) What relationship is explained using Newton’s Second Law.
5) What is Newton’s 1st Law and how is it related to inertia.

2. 6) Be able to apply Newton’s 2nd Law to solve for force problems.
7) Describe how mass, weight, and Newton’s 2nd Law are related.
8) Compare and Contrast “drag force” from “terminal velocity.”
9) Define Newton’s 3rd Law.

3. 10) Be able to solve problems involving force pairs.
11) What is a “Normal Force.”
12) Determine Normal Force for an object on an incline.

4. Chapter 4: Forces in One Dimension
I) Force and Motion
A)    Force and Motion
1) _ _ _ _ _ : a push or pull on an object that could change the object’s motion.

5. 2) The Units:
3) Scalar or Vector?
B) Contact Forces and Field Forces
1) Contact Force: Two or more objects in physical contact.

6. a) Field forces include:
2) Field Force: Forces that exist between objects, even in the absence of physical contact between the objects
a) Field forces include:
E-Field Demo

7. 3) Free-body Diagram:
“picture yourself holding a baseball at rest in your hand”

8. C) Force and Acceleration
1) A quick experiment:
Push on a cart and observe its motion.
Push a little harder on the car (increase your applied force) and observe its motion.
a) As the force applied to an object increases, the acceleration:

9. Add a mass to the cart and push on it with your original force.
b) As the mass of an object increases, its acceleration:
D) Newton’s Second Law

10. “The relationship between mass, net force, and acceleration.”
1) Newton’s 2nd Law Equation:
a) Units of force:

11. E) Combining Forces
1) _ _ _ _ _ _ _ _ : the vector sum of all forces acting on an object; also known as the resultant.
a) Example:

12. F) Newton’s First Law
1) Newton’s 1st Law: an object will continue in its present state of motion unless acted upon by a net external force.
a) The tablecloth demo!
b) _ _ _ _ _ _ _ : the tendency of an object to resist changes in its motion. “Why it is more difficult to get an object to start moving than it is to keep it moving.”

13. 2) Equilibrium: when all the forces acting on an object add to zero; they cancel out.
a) List two example of equilibrium!

14. II) Using Newton’s Laws
A) Using Newton’s Second Law:

15. 1) Sample Problem: “Oranjello is learning to skate
1) Sample Problem: “Oranjello is learning to skate. He has his mother push him so that he accelerates across the ice at 0.75 m/s*s. If Oranjello has a mass of 29.0 kg, with what force must his mother push him?”

16. 2)  _ _ _ _ _ _ : the product of the mass of an object and the acceleration due to gravity it experiences.
 a) The Formula:

17. 3) Apparent Weight and Weightlessness:
a) The elevator moves upward:
“Your mass is 75.0 kg and your standing on a bathroom scale in an elevator that accelerates upward at 2.00 m/s2. a) What’s your normal weight? b) What’s your weight during the upward acceleration?”

19. b) The elevator cable breaks; weightlessness.

20. B) Drag Force and Terminal Velocity:
1) Drag Force: the force exerted by a fluid ( _ _ _ or _ _ _ _ _ _ ) on an object moving through the fluid.

21. a) What happens to the drag force as a tennis ball falls through the air:

22. b) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ : The constant velocity reached by a falling object when its weight equals the drag force it encounters.

23. III) Interaction Forces
A) Identifying Interaction Forces
1) “Forces always come in “
a) You push on a wall (lean on the wall), the wall ….

24. B) Newton’s Third Law
1) Newton’s 3rd Law: For every Action force, there is an equal and opposite Reaction force.
a) The equation:

25. b) Sample Problem: “When a softball with a mass of 0
b) Sample Problem: “When a softball with a mass of 0.25 kg is dropped toward the ground, the earth is pulled up to the softball. What’s the resulting acceleration of the earth?” **mass of earth equals 6.0 X 1024 kg.

26. C) Forces of Ropes and Strings
1) What’s the tension(s) in the diagrams below?

27. 2) Sample Problem: “A 50 kg bucket is being lifted by a rope
2) Sample Problem: “A 50 kg bucket is being lifted by a rope. The rope will not break if the tension doesn’t exceed 525 N. The bucket started from rest, and after being lifted 3.0 m, is moving at 3.0 m/s. If the acceleration is constant, is the rope in danger of breaking?”

29. D) Normal Force
1) Normal Force: The perpendicular contact force exerted by a surface on another object.