2 Motion 3 Acceleration 4(A) MAINIDEA Write the Main Idea for this lesson. REVIEW VOCABULARY Recall the definition of the Review Vocabulary term. velocity velocity NEW VOCABULARY Use your book to define the terms below. acceleration acceleration centripetal acceleration centripetal acceleration ACADEMIC VOCABULARY Use a dictionary to define constant to its scientific meaning. constant constant Science Notebook • Motion 26 Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use. Analyze why we say an object is accelerating, when we usually mean that it is speeding up. An object that is slowing down also is accelerating. 3 Acceleration (continued) Student Edition, pp. 56–58 Reading Essentials, pp. 36–38 Analyze Label each of the four parts of the graph with either a plus sign, a minus sign, or a zero to indicate where the car’s acceleration is positive, negative, or zero. Velocity and Acceleration Speed Speed Changing Over Time 1 2 3 4 5 6 7 8 9 10min Time • Describe the relationship between speed and acceleration as shown in your graph. Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use. GET IT? Motion in Two Dimensions Identify three ways that an object can accelerate. Compare the results of applying the acceleration equation in the following two cases: (1) an object that goes from 0 to 10 m/s in 4 s, and (2) then goes from 10 m/s to 30 m/s in 8 s. (1) a = (vf – vi)/t = = (2) a = (vf – vi )/t = Science Notebook • Motion 27 = 3 Acceleration (continued) Student Edition, pp. 58–59 Analyze why the SI unit of acceleration is m/s2. Reading Essentials, pp. 38–39 Circular Motion Create a top view of an object moving in a circle at constant speed, such as a ball on a string. Show at least two positions of the object. At each position, draw an arrow for the object’s velocity and another arrow for the centripetal acceleration of the object. Define the term centripetal acceleration. Science Notebook • Motion 28 Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use. GET IT? 3 Acceleration (continued) Student Edition, pp. 59–60 Reading Essentials, pp. 39–40 Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use. Projectile Motion Model a ball thrown horizontally. Sketch the path of the ball and draw arrows showing its horizontal and vertical velocity at three points along the path. Vary the length of your arrows to show the magnitude of the velocities. SYNTHESIZE IT Distinguish between average acceleration and instantaneous acceleration. Be sure to explain how the acceleration equation calculates average acceleration, instantaneous acceleration, or both. Science Notebook • Motion 29 3 Acceleration (continued) REVIEW IT ! 25. MAINIDEA Describe the acceleration of your bicycle as you ride it from your home to the store. 26. Determine the change in velocity of a car that starts at rest and has a final velocity of 20 m/s north. 27. Describe the motion of an object that has an acceleration of 0 m/s2. 28. Think Critically Suppose a car traveling in a straight line is accelerating so that its speed is increasing. First, describe the line that you would plot on a speed-time graph for the motion of the car. Then describe the line that you would plot on a distance-time graph. 30. Calculate Speed A sprinter leaves the starting blocks with an acceleration of 4.5 m/s2. What is the sprinter’s speed 2 s later? Science Notebook • Motion 30 Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use. 29. Calculate Time A ball is dropped from a cliff and has an acceleration of 9.8 m/s2. How long will it take the ball to reach a speed of 24.5 m/s?

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