Chapter 9 Motion and Energy. Table of Contents. Chapter Preview. 9.1 Describing Motion. 9.2 Speed and Velocity. 9.3 Acceleration. 9.

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1 Table of Contents Chapter Preview 9.1 Describing Motion 9.2 Speed and Velocity 9.3 Acceleration 9.4 Energy

2 Chapter Preview Questions 1. Is a moving bus a good reference point from which to measure your position? a. No, because it is often late. b. No, because it is not a stationary object. c. Yes, because it is very large. d. Yes, because it can travel very far.

3 Chapter Preview Questions 1. Is a moving bus a good reference point from which to measure your position? a. No, because it is often late. b. No, because it is not a stationary object. c. Yes, because it is very large. d. Yes, because it can travel very far.

4 Chapter Preview Questions 2. To describe a friend s position with respect to you, you need to know a. Your friend s distance from you. b. The direction your friend is facing. c. Your friend s distance and direction from you. d. Your friend s distance from a nearby object.

5 Chapter Preview Questions 2. To describe a friend s position with respect to you, you need to know a. Your friend s distance from you. b. The direction your friend is facing. c. Your friend s distance and direction from you. d. Your friend s distance from a nearby object.

6 Chapter Preview Questions 3. Two cars traveling in the same direction pass you at exactly the same time. The car that is going faster a. moves farther in the same amount of time. b. has more mass. c. has the louder engine. d. has less momentum.

7 Chapter Preview Questions 3. Two cars traveling in the same direction pass you at exactly the same time. The car that is going faster a. moves farther in the same amount of time. b. has more mass. c. has the louder engine. d. has less momentum.

8 Chapter Preview Questions 4. To describe an object s motion, you need to know its a. position. b. change in position. c. distance. d. change in position over time.

9 Chapter Preview Questions 4. To describe an object s motion, you need to know its a. position. b. change in position. c. distance. d. change in position over time.

10 How can you describe an object s motion? You are in a stationary car and another car passes you. How would you describe the motion of the other car?

11 Use Related Words Word Definition Example Sentence conclude v. to decide by reasoning After investigating the evidence, they concluded that everyone should wear a bicycle helmet.

12 Use Related Words Word Definition Example Sentence formula n. a series of numbers and symbols that represents a mathematical rule The formula for the area of a circle is A = πr 2.

13 Use Related Words Word Definition Example Sentence potential adj. the possibility that something will develop in a certain way The student who is studying chemistry is a potential chemist.

14 Apply It! Choose the word from the table that best completes the sentence. 1. The for finding the area of a rectangle is A = l x w. formula 2. After waiting for 20 minutes, he that his friend was not coming. concluded 3. The heavy rains and rising river are a problem for people who live beside the river. potential

15 End of Chapter Preview

16 Section 1: Describing Motion When is an object in motion? What is the difference between distance and displacement?

17 - Describing Motion Whether or not an object is in motion depends on the reference point you choose. Relative Motion

18 Distance and Displacement Distance is the total length of the actual path between two points. Displacement is the length and direction of a straight line between starting and ending points.

19 End of Section: Describing Motion

20 Section 2: Speed and Velocity When is an object in motion? What is the difference between distance and displacement?

21 Calculating Speed If you know the distance an object travels in a certain amount of time, you can calculate the speed of the object.

22 Graphing Motion You can use distance-versus-time graphs to interpret motion.

23 Graphing Motion Activity Click the Active Art button to open a browser window and access Active Art about graphing motion.

24 Velocity Click the Video button to watch a movie about velocity.

25 End of Section: Speed and Velocity

26 Section 3: Acceleration What kind of motion does acceleration refer to? How do you calculate acceleration? What graphs can be used to analyze the motion of an accelerating object?

27 Calculating Acceleration To determine the acceleration of an object, you must calculate its change in velocity per unit of time.

28 Calculating Acceleration As a roller-coaster car starts down a slope, its velocity is 4 m/s. But 3 seconds later, its velocity is 22 m/s in the same direction. What is its acceleration? Read and Understand What information have you been given? Initial velocity = 4 m/s Final velocity = 22 m/s Time = 3 s

29 Calculating Acceleration As a roller-coaster car starts down a slope, its velocity is 4 m/s. But 3 seconds later, its velocity is 22 m/s in the same direction. What is its acceleration? Plan and Solve What quantity are you trying to calculate? The acceleration of the roller-coaster car = What formula contains the given quantities and the unknown quantity? Acceleration = (Final velocity - Initial velocity)/time Perform the calculation. Acceleration = (22 m/s - 4 m/s)/3 s = 18 m/s/3 s Acceleration = 6 m/s 2 The acceleration is 6 m/s 2 down the slope.

30 Calculating Acceleration As a roller-coaster car starts down a slope, its velocity is 4 m/s. But 3 seconds later, its velocity is 22 m/s in the same direction. What is its acceleration? Look Back and Check Does your answer make sense? The answer is reasonable. If the car s velocity increases by 6 m/s each second, its velocity will be 10 m/s after 1 second, 16 m/s after 2 seconds, and 22 m/s after 3 seconds.

31 Calculating Acceleration Practice Problem A falling raindrop accelerates from 10 m/s to 30 m/s in 2 seconds. What is the raindrop s acceleration? (30 m/s - 10 m/s) 2 seconds = 10 m/s 2

32 Calculating Acceleration Practice Problem A certain car can accelerate from rest to 27 m/s in 9 seconds. Find the car s acceleration. (27 m/s - 0 m/s) 9 s = 27 m/s 9 s = 3 m/s 2

33 Graphing Acceleration You can use both a speed-versus-time graph and a distanceversus-time graph to analyze the motion of an accelerating object.

34 Links on Acceleration Click the SciLinks button for links on acceleration.

35 End of Section: Acceleration

36 Section 4: Energy What factors affect an object s kinetic energy and potential energy? How can kinetic energy and potential energy be transformed? What is the law of conservation of energy?

37 Exponents An exponent tells how many times a number is used as a factor. For example, 3 x 3 can be written as 3 2. You read this number as three squared. In the formula for kinetic energy, speed is squared. For example, you can calculate the kinetic energy of a 70-kg person moving at a speed of 2 m/s by using the formula below. KE = ½ x Mass x Speed 2 = ½ x 70 kg x (2 m/s) 2 = 140 kg m 2 /s 2 or 140 joules. Note: 1 kg m 2 /s 2 = 1 joule

38 Practice Problem Exponents What is the kinetic energy of a 30-kg rock moving at a speed of 10 m/s? 1,500 joules

39 Kinetic Energy Kinetic energy increases as mass and speed increase.

40 Potential Energy Gravitational potential energy increases as weight and height increase.

41 Transformations Between Potential and Kinetic Energy A pendulum continuously transforms energy from kinetic to potential energy and back.

42 Energy Transformations Activity Click the Active Art button to open a browser window and access Active Art about energy transformations.

43 Links on Energy Click the SciLinks button for links on energy.

44 Links on Forms of Energy Click the SciLinks button for links on forms of energy.

45 End of Section: Energy

46 QuickTake Quiz Click to start quiz.

KINETIC AND POTENTIAL ENERGY. Chapter 6 (cont.)

KINETIC AND POTENTIAL ENERGY. Chapter 6 (cont.) KINETIC AND POTENTIAL ENERGY Chapter 6 (cont.) The Two Types of Mechanical Energy Energy- the ability to do work- measured in joules Potential Energy- energy that arises because of an object s position