1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Motion Chapter 10 Table of Contents Section 1 Measuring Motion Section 2 Acceleration Section 3 Motion and Force

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Chapter 10

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Bellringer Everybody knows what motion is, but how do you measure it? One way is to measure distance, how far something goes during a motion. Another is to measure time, how long a motion takes to occur. A third way is to measure speed, how fast something is moving. Each of the devices shown below can be used to measure some aspect of motion. Section 1 Measuring Motion Chapter 10

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Bellringer, continued 1.For each of the devices above, indicate whether it measures distance, time, or speed. 2.For each of the devices above, indicate which of the following units are possible for a measurement: meters (m), seconds (s), or meters per second (m/s). Section 1 Measuring Motion Chapter 10

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Section 1 Measuring Motion Chapter 10

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Distance vs. Displacement Section 1 Measuring Motion Chapter 10

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Section 1 Measuring Motion Chapter 10

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Section 1 Measuring Motion Chapter 10

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Speed and Velocity, continued Average speed is calculated as distance divided by time. Equation for Average Speed Section 1 Measuring Motion Chapter 10 Instantaneous speed is the speed at a given point in time.

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. 1.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) Section 1 Measuring Motion Chapter 10

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Math Skills, continued 2. Perform any necessary conversions. To find the velocity in meters per second, the value for time must be in seconds. Section 1 Measuring Motion Chapter 10

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Math Skills, continued 3. Write the equation for speed. Section 1 Measuring Motion Chapter 10 4. Insert the known values into the equation, and solve.

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Section 1 Measuring Motion Chapter 10

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Chapter 10

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Bellringer Which of the following examples shows a change in velocity? Remember a change in velocity can be either a change in speed or a change in the direction of motion. Briefly explain your answer. a. a car coming to a stop at a stop sign b. a book sitting on a desk c. a yo-yo in motion d. a bicyclist making a left-hand turn at exactly 15 km/h Section 2 Acceleration Chapter 10

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Bellringer, continued In the picture shown above, the student pulls on the box with the rope. If the box is originally not moving, will its velocity increase or stay the same? In which direction (if any) will the velocity be after the student pulls on the box with the rope? Section 2 Acceleration Chapter 10

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Acceleration and Motion Acceleration is the rate at which velocity changes over time. An object accelerates if its speed, direction, or both change. Section 2 Acceleration Chapter 10

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Acceleration and Motion, continued Acceleration can be a change in speed. Acceleration can be a change in direction. Uniform circular motion is constant acceleration. Section 2 Acceleration Chapter 10

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Acceleration is the rate at which velocity changes. Acceleration Equation (for straight-line motion) Section 2 Acceleration Chapter 10 Calculating Acceleration In SI units, acceleration is measured in meters per second per second (m/s/s) or m/s 2.

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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, v i = 0 m/s final velocity, v f = 14.7 m/s down Unknown: acceleration, a = ? (m/s 2 and direction) Section 2 Acceleration Chapter 10

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Math Skills, continued 3. Insert the known values into the equation, and solve. Section 2 Acceleration Chapter 10 2. Write the equation for acceleration.

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Calculating Acceleration, continued Acceleration can be determined from a velocity-time graph. Section 2 Acceleration Chapter 10

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Chapter 10

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The concept of force explains many occurrences in our everyday lives. From your own experience, state what will happen in the following situations: 1.A marble is placed at the top of a smooth ramp. What happens to the marble? What force causes this? 2.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.) 3.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? Section 3 Motion and Force Chapter 10 Bellringer

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Section 3 Motion and Force Chapter 10

26. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Force of Friction Friction is a force that opposes motion between two surfaces that are in contact. Friction opposes the applied force. Section 3 Motion and Force Chapter 10

27. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Section 3 Motion and Force Chapter 10

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Frictional Forces and Acceleration Section 3 Motion and Force Chapter 10

29. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Section 3 Motion and Force Chapter 10

30. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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/s 2 B.–2.5 m/s 2 C.0 m/s 2 D.2.5 m/s 2 Standardized Test Prep Chapter 10

31. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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/s 2 B.–2.5 m/s 2 C.0 m/s 2 D.2.5 m/s 2 Standardized Test Prep Chapter 10

32. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Standardized Test Prep Chapter 10

33. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Standardized Test Prep Chapter 10

34. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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 Standardized Test Prep Chapter 10

35. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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 Standardized Test Prep Chapter 10

36. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts, continued 4. When describing the motion of an object, why do you need a reference point? Standardized Test Prep Chapter 10

37. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Standardized Test Prep Chapter 10

38. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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? Standardized Test Prep Chapter 10

39. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Standardized Test Prep Chapter 10

40. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Standardized Test Prep Chapter 10

41. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Standardized Test Prep Chapter 10

42. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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. Standardized Test Prep Chapter 10

43. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Interpreting Graphics Base you answers to questions 7 and 8 on the graph below, which shows distance (m) versus time (s). Standardized Test Prep Chapter 10

44. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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 Standardized Test Prep Chapter 10

45. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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 Standardized Test Prep Chapter 10

46. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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 Standardized Test Prep Chapter 10

47. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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 Standardized Test Prep Chapter 10