1. Module 2, Recitation 2 Concept questions on v-t graphs

2. ConcepTest Graphing Velocity I t x The graph of position versus time for a car is given below. What can you say about the velocity of the car over time? The graph of position versus time for a car is given below. What can you say about the velocity of the car over time? 1) it speeds up all the time 2) it slows down all the time 3) it moves at constant velocity 4) sometimes it speeds up and sometimes it slows down 5) not really sure

3. ConcepTest Graphing Velocity I t x The graph of position versus time for a car is given below. What can you say about the velocity of the car over time? The graph of position versus time for a car is given below. What can you say about the velocity of the car over time? The car moves at a constant velocity because the x vs. t plot shows a straight line. The slope of a straight line is constant. Remember that the slope of x versus t is the velocity! 1) it speeds up all the time 2) it slows down all the time 3) it moves at constant velocity 4) sometimes it speeds up and sometimes it slows down 5) not really sure

4. t x 1) it speeds up all the time 2) it slows down all the time 3) it moves at constant velocity 4) sometimes it speeds up and sometimes it slows down 5) not really sure The graph of position vs. time for a car is given below. What can you say about the velocity of the car over time? The graph of position vs. time for a car is given below. What can you say about the velocity of the car over time? ConcepTestGraphing Velocity II

5. 1) it speeds up all the time 2) it slows down all the time 3) it moves at constant velocity 4) sometimes it speeds up and sometimes it slows down 5) not really sure t x The graph of position vs. time for a car is given below. What can you say about the velocity of the car over time? The graph of position vs. time for a car is given below. What can you say about the velocity of the car over time? The car slows down all the time because the slope of the x vs. t graph is diminishing as time goes on. Remember that the slope of x vs. t is the velocity! At large t, the value of the position x does not change, indicating that the car must be at rest. ConcepTestGraphing Velocity II

6. Consider the v versus t plot. How does the speed change with time? Consider the v versus t plot. How does the speed change with time? v t 1) decreases 2) increases 3) stays constant 4) increases, then decreases 5) decreases, then increases ConcepTestv versus t graphs I

7. Consider the v versus t plot. How does the speed change with time? Consider the v versus t plot. How does the speed change with time? v t 1) decreases 2) increases 3) stays constant 4) increases, then decreases 5) decreases, then increases The initial velocity is positive and the magnitude of the velocity continues to increase with time. ConcepTestv versus t graphs I

8. Consider the v versus t plot. How does the speed change with time? Consider the v versus t plot. How does the speed change with time? v t 1) decreases 2) increases 3) stays constant 4) increases, then decreases 5) decreases, then increases ConcepTestv versus t graphs II

9. Consider the v versus t plot. How does the speed change with time? Consider the v versus t plot. How does the speed change with time? v t 1) decreases 2) increases 3) stays constant 4) increases, then decreases 5) decreases, then increases The initial velocity is positive but the magnitude of the velocity decreases toward zero. After this, the magnitude increases again, but becomes negative, indicating that the object has changed direction. ConcepTestv versus t graphs II

10. ConcepTest Rubber Balls I v t 1 v t 2 v t 3 v t 4 You drop a rubber ball. Right after it leaves your hand and before it hits the floor, which of the above plots represents the v vs. t graph for this motion? (Assume your y-axis is pointing up). You drop a rubber ball. Right after it leaves your hand and before it hits the floor, which of the above plots represents the v vs. t graph for this motion? (Assume your y-axis is pointing up).

11. ConcepTest Rubber Balls I v t 1 v t 2 v t 3 v t 4 You drop a rubber ball. Right after it leaves your hand and before it hits the floor, which of the above plots represents the v vs. t graph for this motion? (Assume your y- axis is pointing up). You drop a rubber ball. Right after it leaves your hand and before it hits the floor, which of the above plots represents the v vs. t graph for this motion? (Assume your y- axis is pointing up). initial velocity is zero velocity is negativemore and more negative The ball is dropped from rest, so its initial velocity is zero. Since the y-axis is pointing upwards and the ball is falling downwards, its velocity is negative and becomes more and more negative as it accelerates downward.

12. v t 4 v t 2 v t 3 v t 1 You toss a ball straight up in the air and catch it again. Right after it leaves your hand and before you catch it, which of the above plots represents the v vs. t graph for this motion? (Assume your y- axis is pointing up). You toss a ball straight up in the air and catch it again. Right after it leaves your hand and before you catch it, which of the above plots represents the v vs. t graph for this motion? (Assume your y- axis is pointing up). ConcepTest ConcepTestRubber Balls II

13. v t 4 v t 2 v t 3 v t 1 You toss a ball straight up in the air and catch it again. Right after it leaves your hand and before you catch it, which of the above plots represents the v vs. t graph for this motion? (Assume your y-axis is pointing up). You toss a ball straight up in the air and catch it again. Right after it leaves your hand and before you catch it, which of the above plots represents the v vs. t graph for this motion? (Assume your y-axis is pointing up). initial velocity that is positive velocity becomes negative more and more negative The ball has an initial velocity that is positive but diminishing as it slows. It stops at the top (v = 0), and then its velocity becomes negative and becomes more and more negative as it accelerates downward. ConcepTest ConcepTestRubber Balls II

14. v t 1 v t 2 v t 3 v t 4 ConcepTest ConcepTestRubber Balls III You drop a very bouncy rubber ball. It falls, and then it hits the floor and bounces right back up to you. Which of the following represents the v vs. t graph for this motion? You drop a very bouncy rubber ball. It falls, and then it hits the floor and bounces right back up to you. Which of the following represents the v vs. t graph for this motion?

15. v t 1 v t 2 v t 3 v t 4 negative increasing positive decreasing Initially, the ball is falling down, so its velocity must be negative (if UP is positive). Its velocity is also increasing in magnitude as it falls. Once it bounces, it changes direction and then has a positive velocity, which is also decreasing as the ball moves upward. ConcepTest ConcepTestRubber Balls III

16. Module 2, Recitation 2 Match the s-v-a vs. t graphs of Pasco car motion

17. Track 1: Level track, spring plunger on one end and Velcro on the other. Start the car in the center of the track and give it a gentle push towards the end with the plunger. Plot graphs for the motion from when you finish pushing the car until it stops. Insert graph from Data Studio of position-velocity-acceleration

18. Track 2: Level track, fan accessory. Start car at left end. The fan is set to be on for 1 second. Plot graphs for the motion from when the fan starts until the car reaches the right end of the track. Insert graph from Data Studio of position-velocity-acceleration

19. Track 3: Inclined track, spring plunger. Let the car roll down the track and bounce off the end several times. Insert graph from Data Studio of position-velocity-acceleration

20. Track 4: Inclined track; small, and large sails. Plot the motion from when released until the car reaches the end of the track. Compare motion for no sail (track 3), the small sail, and the large sail. Insert graph from Data Studio of position-velocity-acceleration

21. Module 2, Recitation 2 Match the amusement park acceleration graphs

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