6 Motion in Two Dimensions BIGIDEA Write the Big Idea for this chapter.

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1 6 Motion in Two Dimensions BIGIDEA Write the Big Idea for this chapter. Use the What I Know column to list the things you know about the Big Idea. Then list the questions you have about the Big Idea in the What I Want to Find Out column. As you read the chapter, fill in the What I Learned column. K What I Know W What I Want to Find Out L What I Learned 89

2 6 Motion in Two Dimensions 1 Projectile Motion 4(C) MAINIDEA Write the Main Idea for this section. REVIEW VOCABULARY motion diagram Recall and write the definition of the Review Vocabulary term. motion diagram NEW VOCABULARY projectile trajectory Use your book to define each term. projectile trajectory 90

3 Student Edition, pp Draw an illustration of a softball gently tossed from one player to another. Label the projectile and the trajectory in the illustration. Identify the only force acting on a tossed ball (ignoring air resistance). Compare the horizontal motion and the vertical motion of the balls in Figure 2. GET IT? Explain why a dropped object has the same vertical velocity as an object launched horizontally. Complete the sentences to make them true. In a horizontally launched projectile, the x- and y-components can be treated. The resultant vectors of the projectile are to a. 91

4 Student Edition, pp Describe a scenario in which the diagram in Figure 3 could be used to describe the motion of an object. GET IT? Explain why the horizontal motion of a projectile is constant. Explain why a horizontally launched projectile has a parabolic shape. Describe the significance of symmetry in the path of an object launched straight up in the air. Identify two important components in the path of an object launched at an angle. GET IT? Identify At what point of a projectile s trajectory is its vertical velocity zero? 92

5 Student Edition, p. 157 Use with Example Problem 2. Use this column for scratch work and sketches. TRY IT! Problem THE FLIGHT OF A BALL A ball is launched at 5.5 m/s at 76 above the horizontal. It starts and lands at the same distance from the ground. What are the maximum height above its launch level and the flight time of the ball? 1. ANALYZE AND SKETCH THE PROBLEM KNOWNS UNKNOWNS y i = θ = =? v i = a y = =? v y, max = 2. SOLVE FOR THE UNKNOWNS Find the y-component of v i. Use symmetry to find the y-component of v f. Solve for the maximum height. Solve for the time to return to the launching height. 3. EVALUATE THE ANSWER Are the magnitudes realistic? 93

6 Student Edition, p. 158 Draw three pictures below showing how moving air affects water flowing from a water hose. Use vectors to show motion. No Effect from Air Force of Air that Increases Velocity Force of Air that Decreases Velocity SUMMARIZE How does the MAINIDEA for this section relate to the chapter s BIGIDEA? REVIEW IT! 7. MAINIDEA Two baseballs are pitched horizontally from the same height but at different speeds. The faster ball crosses home plate within the strike zone, but the slower ball is below the batter s knees. Why do the balls pass the batter at different heights? 94

7 8. Free-Body Diagram An ice cube slides without friction across a table at a constant velocity. It slides off the table and lands on the floor. Draw free-body and motion diagrams of the ice cube at two points on the table and at two points in the air. 9. Projectile Motion A tennis ball is thrown out a window 28 m above the ground at an initial velocity of 15.0 m/s and 20.0 below the horizontal. How far does the ball move horizontally before it hits the ground? 10. Projectile Motion A softball player tosses a ball into the air with an initial velocity of 11.0 m/s, as shown in Figure 7. What will be the ball s maximum height? Figure Critical Thinking Suppose an object is thrown with the same initial velocity and direction on Earth and on the Moon, where the acceleration due to gravity is one-sixth its value on Earth. How will vertical velocity, time of flight, maximum height, and horizontal distance change? 95