1. Chapter 10
Section 1 Measuring Motion
Objectives
Explain the relationship between motion and a frame of reference.
Relate speed to distance and time.
Distinguish between speed and velocity.
Solve problems related to time, distance, displace-ment, speed, and velocity.

2. Chapter 10 Observing Motion
Section 1 Measuring Motion
Observing Motion
Motion is an object’s change in position relative to a reference point.
Displacement is the change in the position of an object.
Distance measures the path taken.
Displacement is the change of an object’s position. Displacement must always indicate direction.

3. Chapter 10
Section 1 Measuring Motion
Motion

4. Distance vs. Displacement
Chapter 10
Section 1 Measuring Motion
Distance vs. Displacement
Teaching Transparency

5. Chapter 10 Speed and Velocity
Section 1 Measuring Motion
Speed and Velocity
Speed is the distance traveled divided by the time interval during which the motion occurred. Speed describes how fast an object moves.
Speed measurements involve distance and time.
The SI units for speed are meters per second (m/s).
When an object covers equal distances in equal amounts of time, it is moving at a constant speed.

6. Chapter 10
Section 1 Measuring Motion
Speed

7. Speed and Velocity, continued
Chapter 10
Section 1 Measuring Motion
Speed and Velocity, continued
Speed can be studied with graphs and equations.
Speed can be determined from a distance-time graph. When an object’s motion is graphed by plotting distance on the y-axis and time on the x-axis, the slope of the graph is speed.

8. Speed and Velocity, continued
Chapter 10
Section 1 Measuring Motion
Speed and Velocity, continued
Average speed is calculated as distance divided by time.
Equation for Average Speed
Instantaneous speed is the speed at a given point in time.

9. Chapter 10
Section 1 Measuring Motion
Math Skills
Velocity Metal stakes are sometimes placed in glaciers to help measure a glacier’s movement. For several days in 1936, Alaska’s Black Rapids glacier surged as swiftly as 89 meters per day down the valley. Find the glacier’s velocity in m/s. Remember to include direction.
List the given and the unknown values.
Given: time, t = 1 day
displacement, d = 89 m down the valley
Unknown: velocity, v = ? (m/s and direction)

10. Chapter 10 Math Skills, continued
Section 1 Measuring Motion
Math Skills, continued
2. Perform any necessary conversions.
To find the velocity in meters per second, the value for time must be in seconds.

11. Chapter 10 Math Skills, continued 3. Write the equation for speed.
Section 1 Measuring Motion
Math Skills, continued
3. Write the equation for speed.
4. Insert the known values into the equation, and solve.

12. Speed and Velocity, continued
Chapter 10
Section 1 Measuring Motion
Speed and Velocity, continued
Velocity is the speed of an object in a particular direction.
Velocity describes both the speed and the direction.
Combine velocities to determine the resultant velocity.

13. Speed and Velocity, continued
Chapter 10
Section 1 Measuring Motion
Speed and Velocity, continued

14. Chapter 10 Velocity Section 1 Measuring Motion
Click below to watch the Visual Concept.
Visual Concept

15. Chapter 10
Section 2 Acceleration
Objectives
Describe the concept of acceleration as a change in velocity.
Explain why circular motion is continuous acceleration even when the speed does not change.
Calculate acceleration as the rate at which velocity changes.
Graph acceleration on a velocity-time graph.

16. Acceleration and Motion
Chapter 10
Section 2 Acceleration
Acceleration and Motion
Acceleration is the rate at which velocity changes over time.
An object accelerates if its speed, direction, or both change.

17. Chapter 10
Section 2 Acceleration
Acceleration

18. Acceleration and Motion, continued
Chapter 10
Section 2 Acceleration
Acceleration and Motion, continued
Acceleration can be a change in speed.
Acceleration can be a change in direction.
Uniform circular motion is constant acceleration.

19. Centripetal Acceleration
Chapter 10
Section 2 Acceleration
Centripetal Acceleration

20. Calculating Acceleration
Chapter 10
Section 2 Acceleration
Calculating Acceleration
Acceleration is the rate at which velocity changes.
Acceleration Equation (for straight-line motion)
In SI units, acceleration is measured in meters per second per second (m/s/s) or m/s2.

21. Chapter 10
Section 2 Acceleration
Math Skills
Acceleration A flowerpot falls off a second-story windowsill. The flowerpot starts from rest and hits the sidewalk 1.5 s later with a velocity of 14.7 m/s. Find the average acceleration of the flowerpot.
1. List the given and the unknown values.
Given: time, t = 1.5 s
initial velocity, vi = 0 m/s
final velocity, vf = 14.7 m/s down
Unknown: acceleration, a = ? (m/s2 and direction)

22. Chapter 10 Math Skills, continued
Section 2 Acceleration
Math Skills, continued
2. Write the equation for acceleration.
3. Insert the known values into the equation, and solve.

23. Calculating Acceleration, continued
Chapter 10
Section 2 Acceleration
Calculating Acceleration, continued
Acceleration can be determined from a velocity-time graph.

24. Graphical Representations of Acceleration
Chapter 10
Section 2 Acceleration
Graphical Representations of Acceleration

25. Chapter 10
Section 3 Motion and Force
Objectives
Explain the effects of unbalanced forces on the motion of objects.
Compare and contrast static and kinetic friction.
Describe how friction may be either harmful or helpful.
Identify ways in which friction can be reduced or increased.

26. Chapter 10 Bellringer Section 3 Motion and Force
The concept of force explains many occurrences in our everyday lives. From your own experience, state what will happen in the following situations:
A marble is placed at the top of a smooth ramp. What happens to the marble? What force causes this?
A marble is rolling around in the back of a small toy wagon as the wagon is pulled along the sidewalk. When the wagon is stopped suddenly by a rock under one of the wheels, the marble rolls towards the front of the wagon. Why does the marble keep going when the wagon stops? (Hint: Consider what it takes to change the velocity of the wagon and the marble.)
If you dropped a flat uncrumpled sheet of notebook paper and a similar piece of notebook paper that was crushed into a ball from the same height, which would reach the floor first? Why are the forces on these two pieces of paper different?

27. Balanced and Unbalanced Forces
Chapter 10
Section 3 Motion and Force
Balanced and Unbalanced Forces
Force is an action exerted on a body in order to change the body’s state of rest or motion. Force has magnitude and direction.
The net force is the combination of all forces acting on an object.
Objects subjected to balanced forces either do not move or move at constant velocity.
An unbalanced force must be present to cause any change in an object’s state of motion or rest.

28. Chapter 10
Section 3 Motion and Force
Force

29. Chapter 10 The Force of Friction
Section 3 Motion and Force
The Force of Friction
Friction is a force that opposes motion between two surfaces that are in contact.
Friction opposes the applied force.

30. The Force of Friction, continued
Chapter 10
Section 3 Motion and Force
The Force of Friction, continued

31. The Force of Friction, continued
Chapter 10
Section 3 Motion and Force
The Force of Friction, continued
Static friction resists the initiation of sliding motion between two surfaces that are in contact and at rest.
Kinetic friction opposes the movement of two surfaces that are in contact and are sliding over each other.
Static friction is greater than kinetic friction.
There are many different types of kinetic friction, such as sliding friction and rolling friction.
Fluid friction, such as air resistance, also opposes motion.

32. Chapter 10
Section 3 Motion and Force
Types of Friction

33. Frictional Forces and Acceleration
Chapter 10
Section 3 Motion and Force
Frictional Forces and Acceleration

34. Chapter 10 Friction and Motion Friction can be helpful or harmful.
Section 3 Motion and Force
Friction and Motion
Friction can be helpful or harmful.
Friction is necessary to roll a vehicle or hold an object.
However, friction can also cause excessive heating or wear of moving parts.
Harmful friction can be reduced.
Helpful friction can be increased.

35. Ways to Reduce or Increase Friction
Chapter 10
Section 3 Motion and Force
Ways to Reduce or Increase Friction

36. Understanding Concepts
Chapter 10
Standardized Test Prep
Understanding Concepts
1. A bicyclist traveling at 10 m/s applies her brakes, reducing her velocity to 5 m/s. If it takes 2 seconds to slow the bike, what is the acceleration during that period?
A. –5 m/s2
B. –2.5 m/s2
C. 0 m/s2
D. 2.5 m/s2

37. Understanding Concepts, continued
Chapter 10
Standardized Test Prep
Understanding Concepts, continued
1. A bicyclist traveling at 10 m/s applies her brakes, reducing her velocity to 5 m/s. If it takes 2 seconds to slow the bike, what is the acceleration during that period?
A. –5 m/s2
B. –2.5 m/s2
C. 0 m/s2
D. 2.5 m/s2

38. Understanding Concepts, continued
Chapter 10
Standardized Test Prep
Understanding Concepts, continued
2. What happens to a moving object when the forces acting on it are exactly balanced?
F. The object gradually slows and stops moving due to friction.
G. The object moves at a constant speed, neither speeding up nor slowing down.
H. The object accelerates because there is no friction to oppose the forces acting on it.
I. The object accelerates because the force of gravity is stronger than friction.

39. Understanding Concepts, continued
Chapter 10
Standardized Test Prep
Understanding Concepts, continued
2. What happens to a moving object when the forces acting on it are exactly balanced?
F. The object gradually slows and stops moving due to friction.
G. The object moves at a constant speed, neither speeding up nor slowing down.
H. The object accelerates because there is no friction to oppose the forces acting on it.
I. The object accelerates because the force of gravity is stronger than friction.

40. Understanding Concepts, continued
Chapter 10
Standardized Test Prep
Understanding Concepts, continued
3. For which of the following is the velocity constant?
A. a baseball traveling away from a bat after a hit
B. a bicyclist on an oval track moving at a constant speed of 15 km/h
C. a helicopter hovering motionless above a fixed point on the ground
D. a canoe being carried down a winding river by a steady current

41. Understanding Concepts, continued
Chapter 10
Standardized Test Prep
Understanding Concepts, continued
3. For which of the following is the velocity constant?
A. a baseball traveling away from a bat after a hit
B. a bicyclist on an oval track moving at a constant speed of 15 km/h
C. a helicopter hovering motionless above a fixed point on the ground
D. a canoe being carried down a winding river by a steady current

42. Understanding Concepts, continued
Chapter 10
Standardized Test Prep
Understanding Concepts, continued
4. When describing the motion of an object, why do you need a reference point?

43. Understanding Concepts, continued
Chapter 10
Standardized Test Prep
Understanding Concepts, continued
4. When describing the motion of an object, why do you need a reference point?
To describe the motion of an object, you need to compare the object’s position to a reference point to determine how the position is changing.

44. Understanding Concepts, continued
Chapter 10
Standardized Test Prep
Understanding Concepts, continued
5. A jet airplane must use a substantial amount of fuel to keep flying at a constant velocity. What two forces would change the velocity of the plane if the engines were shut off?

45. Understanding Concepts, continued
Chapter 10
Standardized Test Prep
Understanding Concepts, continued
5. A jet airplane must use a substantial amount of fuel to keep flying at a constant velocity. What two forces would change the velocity of the plane if the engines were shut off?
Air resistance and the force due to gravity would change the velocity of the plane.

46. Chapter 10 Reading Skills
Standardized Test Prep
Reading Skills
Read the passage below. Then, answer question 6.
Some boats used in calm waters actually float on a cushion of air. A fan blows air below the hull of the craft, while another fan pushes air backward, propelling the boat forward. If the downward fan is turned off, the boat stops moving. The rear-facing fan cannot cause the boat to move until the other fan is turned on again.

47. Reading Skills, continued
Chapter 10
Standardized Test Prep
Reading Skills, continued
6. Demonstrate why the rear-facing fan can accelerate the boat when it is on a cushion of air, but not when it is in contact with the surface of the water.

48. Reading Skills, continued
Chapter 10
Standardized Test Prep
Reading Skills, continued
6. Demonstrate why the rear-facing fan can accelerate the boat when it is on a cushion of air, but not when it is in contact with the surface of the water.
The boat experiences less friction when it is on a cushion of air than it does when it is in contact with the water. The rear-facing fan provides enough force to overcome only the lesser friction.

49. Interpreting Graphics
Chapter 10
Standardized Test Prep
Interpreting Graphics
Base you answers to questions 7 and 8 on the graph below, which shows distance (m) versus time (s).

50. Interpreting Graphics, continued
Chapter 10
Standardized Test Prep
Interpreting Graphics, continued
7. What is the average speed of the runner whose motion is plotted on the graph?
F. 1.0 m/s
G. 1.8 m/s
H. 2.0 m/s
I. 4.5 m/s

51. Interpreting Graphics, continued
Chapter 10
Standardized Test Prep
Interpreting Graphics, continued
7. What is the average speed of the runner whose motion is plotted on the graph?
F. 1.0 m/s
G. 1.8 m/s
H. 2.0 m/s
I. 4.5 m/s

52. Interpreting Graphics, continued
Chapter 10
Standardized Test Prep
Interpreting Graphics, continued
8. During which interval is the runner’s average speed the greatest?
A. 0 s to 5 s
B. 5 s to 10 s
C. 15 s to 20 s
D. 20 s to 25 s

53. Interpreting Graphics, continued
Chapter 10
Standardized Test Prep
Interpreting Graphics, continued
8. During which interval is the runner’s average speed the greatest?
A. 0 s to 5 s
B. 5 s to 10 s
C. 15 s to 20 s
D. 20 s to 25 s