2. Speed vs.Velocity Speed (s) is the distance an object travels per unit of time (rate). Speed (s) is the distance an object travels per unit of time (rate). Velocity (v) describes the speed and direction of a moving object. Velocity (v) describes the speed and direction of a moving object.

3. Velocity Objects undergoing motion will either have a constant or changing velocity Objects undergoing motion will either have a constant or changing velocity constant velocity = not speeding up or slowing down. constant velocity = not speeding up or slowing down. changing velocity = speeding up or slowing down. changing velocity = speeding up or slowing down.

4. Constant / Zero Velocity Distance (m) Time (s) Constant velocity Zero Velocity

5. Changing Velocity Distance (m) Time (s) Speed up Slow Down

6. Average Velocity When working with a constant velocity, we use the following equation. When working with a constant velocity, we use the following equation. ν avg =Δx / Δt Velocity Displacement Time Δ = change

7. Sample Problem What is the velocity of a runner that can travel 10 m in 5 seconds? What is the velocity of a runner that can travel 10 m in 5 seconds? ν avg =Δx / Δt ν avg = 10 m/5 s ν avg = 2 m/s

8. Acceleration changes velocity Acceleration (a): the rate of change of velocity. Acceleration (a): the rate of change of velocity. Objects can accelerate in both the + and - direction. Objects can accelerate in both the + and - direction. Velocity Time

9. Accelerating Car 0 100 Constant acceleration velocity Time

10. Car on cruise control 0 100 Zero Acceleration velocity Time

11. Negative Accelerating Car 0 100 - acceleration velocity Time

12. Acceleration (cont.) a avg = Δ ν /Δt = v f – v i Δt Δt acceleration SI unit = m/s² Final VelocityInitial Velocity

13. Sample Problem A car traveling at 7.0 m/s accelerates uniformly to a velocity of 12.0 m/s in 2.0 s. What is the acceleration of the car? V i = 7 m/s V f = 12 m/s a = v f – v i Δ t Δ t t = 2.0 s = (12.0 m/s – 7.0 m/s) = 2.0 s 2.0 s 2.5 m/s²

14. Changing Acceleration Velocity (v) Time ( Δ t) Forward Motion Reverse Motion Zero Motion

15. 1-Dimentional Motion Equations V avg =Δx/Δt Δx = ½ (v i + v f ) Δt a = (v f - v i ) / Δt Δx = v i Δt + ½ aΔt² v f ² = v i ² + 2aΔx