1. Table of Contents The Nature of Force Friction and Gravity
Newton’s First and Second Laws
Newton’s Third Law
Rockets and Satellites

2. What is a FORCE? - The Nature of Force a push or a pull
vector because they have magnitude (# indicating strength) and a direction 6N
50 N
What are some examples of forces?

3. Named for Sir Isaac Newton Very light, small amt.
What is a Newton?
SI unit of force
Abbreviated N
Named for Sir Isaac Newton
Very light, small amt.
Replaces “pound” in our system
= 1kgm/s2
Measured with a spring scale

4. - The Nature of Force
Combining Forces-The combination of all forces acting on an object is called the net force.

5. Balanced Forces - The Nature of Force
Balanced forces acting on an object do not change the object’s motion.

6. Unbalanced Forces - The Nature of Force
Unbalanced forces acting on an object result in a net force and cause a change in the object’s motion.

7. Balanced and Unbalanced Forces
- The Nature of Force
Balanced and Unbalanced Forces
Use the link to the physics classroom to see how vectors interact.

8. - Newton’s FIRST Law
Law of Inertia

9. Force = mass X acceleration
- - Newton’s Second Law
WRITE DOWN YOUR NEWTON WT.
Force = mass X acceleration
A speedboat pulls a 55-kg water-skier. The force causes the skier to accelerate at 2.0 m/s2. Calculate the net force that causes this acceleration.
Read and Understand
What information have you been given?
Mass of the water-skier (m) = 55 kg
Acceleration of the water-skier (a) = 2.0 m/s2

10. Calculating Force - Newton’s Second Law
A speedboat pulls a 55-kg water-skier. The force causes the skier to accelerate at 2.0 m/s2. Calculate the net force that causes this acceleration.
Plan and Solve
What quantity are you trying to calculate?
The net force (Fnet) = __
What formula contains the given quantities and the unknown quantity?
a = Fnet/m or Fnet = m X a
Perform the calculation.
Fnet = m X a = 55 kg X 2.0 m/s2
F = 110 kg • m/s2
F = 110 N

11. Calculating Force - Newton’s Second Law
A speedboat pulls a 55-kg water-skier. The force causes the skier to accelerate at 2.0 m/s2. Calculate the net force that causes this acceleration.
Look Back and Check
Does your answer make sense?
A net force of 110 N is required to accelerate the water-skier. This may not seem like enough force, but it does not include the force of the speedboat's pull that overcomes friction.

12. Calculating Force Practice Problem - Newton’s Second Law
What is the net force on a 1,000-kg object accelerating at 3 m/s2?
3,000 N (1,000 kg X 3 m/s2)

13. Calculating Force Practice Problem - Newton’s Second Law
What mass can be accelerated
at 14 m/s2 by 350 N?
m= F/a
m= 350 N/14 m/s2
M = 25 kg

14. Newton’s First and Second Laws
Outlining
As you read, make an outline about Newton’s first and second laws. Use the red headings for the main topics and the blue headings for the subtopics.
Newton’s First and Second Laws
Newton’s First Law of Motion
Inertia
Inertia Depends on Mass
The Second Law of Motion
Changes in Force and Mass

15. End of Section: Newton’s First and Second Laws

16. - Newton’s Third Law
Newton’s 3rd Law

17. Calculating Momentum - Newton’s Third Law
Which has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s or a 4.0-kg sledgehammer swung at 0.9 m/s?
Read and Understand
What information have you been given?
Mass of smaller sledgehammer = 3.0 kg
Velocity of smaller sledgehammer = 1.5 m/s
Mass of larger sledgehammer = 4.0 kg
Velocity of larger sledgehammer = 0.9 m/s

18. Calculating Momentum - Newton’s Third Law
Which has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s or a 4.0-kg sledgehammer swung at 0.9 m/s?
Plan and Solve
What quantities are you trying to calculate?
The momentum of each sledgehammer = __
What formula contains the given quantities and the unknown quantity?
Momentum = Mass X Velocity
Perform the calculation.
Smaller sledgehammer = 3.0 km X 1.5 m/s = 4.5 kg•m/s
Smaller sledgehammer = 4.0 km X 0.9 m/s = 3.6 kg•m/s

19. Calculating Momentum - Newton’s Third Law
Which has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s or a 4.0-kg sledgehammer swung at 0.9 m/s?
Look Back and Check
Does your answer make sense?
The 3.0-kg hammer has more momentum than the 4.0-kg one. This answer makes sense because the 3.0-kg hammer is swung at a greater velocity.

20. Calculating Momentum Practice Problem - Newton’s Third Law
A golf ball travels at 16 m/s, while a baseball moves at 7 m/s. The mass of the golf ball is kg and the mass of the baseball is 0.14 kg. Which has the greater momentum?
Golf ball: kg X 16 m/s = 0.72 kg•m/s
Baseball: 0.14 kg X 7 m/s = 0.98 kg•m/s
The baseball has greater momentum.

21. Calculating Momentum Practice Problem - Newton’s Third Law
What is the momentum of a bird with a mass of kg flying at 15 m/s?
0.27 kg•m/s (0.018 kg X 15 m/s = 0.27 kg•m/s)

22. Conservation of Momentum-
- Newton’s Third Law
Conservation of Momentum
In the absence of friction, momentum is conserved when two train cars collide.

23. Conservation of Momentum
- Newton’s Third Law
Previewing Visuals
Before you read, preview Figure 18. Then write two questions that you have about the diagram in a graphic organizer like the one below. As you read, answer your questions.
Conservation of Momentum
Q. What happens when two moving objects collide?
A. In the absence of friction, the total momentum is the same before and after the collision.
Q. What is the momentum of an object?
A. Its mass multiplied by its velocity

24. What Is a Satellite? - Rockets and Satellites
A projectile follows a curved path because the horizontal and vertical motions combine.

25. What Is a Satellite? - Rockets and Satellites
The faster a projectile is thrown, the father it travels before it hits the ground. A projectile with enough velocity moves in a circular orbit.

26. What Is a Satellite? - Rockets and Satellites
Depending on their uses, artificial satellites orbit at different heights.

27. Identifying Main Ideas
- Rockets and Satellites
Identifying Main Ideas
As you read the section “What Is a Satellite?” write the main idea in a graphic organizer like the one below. Then write three supporting details that further explain the main idea.
Main Idea
A satellite stays in orbit due to…
Detail
Detail
Detail
its inertia
Earth’s gravity
Earth’s shape

28. End of Section: Rockets and Satellites

29. Graphic Organizer Type of Friction Occurs When Example Static Sliding
Friction between an unmoving book and desk
An object is not moving
Static
Two solid surfaces slide over each other
Sliding
Rubber pads on a bicycle’s brakes
Rolling
An object rolls across a surface
Ball bearings in skateboard wheels
A solid object moves through a fluid
Fluid
Air resistance

30. End of Section: Graphic Organizer

31. Gravity - Friction and Gravity
Two factors affect the gravitational attraction between objects: mass and distance.
Direct relationship
Indirect relationship

32. Gravity
What has a greater affect on gravitational force: an equal change of mass or distance? (Use the info to the right to help!)

33. Gravity - Friction and Gravity
The force of gravity on a person or object at the surface of a planet is known as weight.

34. Friction
What is it?
Compare the time of a toy car on a smooth track to one on a bumpy track (with sandpaper).
Take 3 trials for each type of track and average them.

35. Friction What is it? What 2 factors does it depend on? 1. 2.
Heat is a by-product of friction.
What types of friction are there? And how do they differ? 3. 4.

36. Free Fall - Friction and Gravity
Use the graph to answer the following questions.

37. Free Fall - Friction and Gravity Interpreting Graphs:
What variable is on the horizontal axis? The vertical axis?
Time is on the horizontal axis, and speed is on the vertical axis.

38. Free Fall - Friction and Gravity Calculating:
Calculate the slope of the graph. What does the slope tell you about the object’s motion?
The slope is 9.8. The speed increases by 9.8 m/s each second.

39. Free Fall - Friction and Gravity Predicting:
What will the speed of the object be at 6 seconds?
58.8 m/s

40. Free Fall - Friction and Gravity Drawing Conclusions:
Suppose another object of the same size but with a greater mass was dropped instead. How would the speed values change?
The speed values would not change.

41. Air Resistance - Friction and Gravity
Falling objects with a greater surface area experience more air resistance.

42. Comparing and Contrasting
- Friction and Gravity
Comparing and Contrasting
As you read, compare and contrast friction and gravity by completing a table like the one below.
Friction
Gravity
Pulls objects toward one another
Effect on motion
Opposes motion
Types of surfaces involved, how hard the surfaces push together
Depends on
Mass and distance
Measured in
Newtons
Newtons