1. Which line represents the greater speed? Graphing motion The greater the speed, the steeper the slope

2. How did the object’s speed change with time? Stopped Velocity 3 Velocity 1 Velocity 2 What’s different about Velocity 2? The object is moving backward.

3. What happened at 4 s? The speed of the object changed

4. What is the average speed? Average speed = total distance/total time = 90 m/10 s = 9 m/s

5. What is the instantaneous speed at 2 s? Instantaneous speed = 5 m/2 s = 2.5 m/s

6. What is the instantaneous speed at 10 s? Instantaneous speed = 90 m/10 s = 9 m/s

7. How is the object moving? It is moving at a constant velocity.

8. How did the object’s motion change? Constant 4 m/s velocity until 4 s, then accelerated for 2 s and then constant 6 m/s velocity

9. What is the acceleration of the object? Acceleration = slope of line = rise/run = (6 - 4)/(8-4) = 0.5 m/s 2 rise run

10. How did the object’s motion change? Constant 8 m/s velocity, then decelerated for 6 s, then constant 2 m/s velocity.

11. What is the acceleration of the object? Acceleration = rise/run = (2-8)/(8-2) = -1 m/s 2 rise run Notice that a negative slope means the object is slowing down.

12. Calculating acceleration: a = v f - v i t 1. A stopped car accelerates to 30 m/s in 15 s. What is its acceleration? V f = 30 m/s v i = 0 m/s t = 15 s a = (30 - 0) = 2 m/s 2 15 2. A car moving at 45 m/s slows to 15 m/s in 5 s. What is its acceleration? V f = 15 m/s v i = 45 m/s t = 5 s a = (15 - 45) = -6 m/s 2 5