1. Motion Chapter 2 Part 1 1

2. What kind of motion will this car undergo? 2

3. Motion is Relative Even things that appear to be at rest move. They move with respect to, or relative to, the sun and stars. Even things that appear to be at rest move. They move with respect to, or relative to, the sun and stars. 3

4. Speed Speed ( v ): The measure of how fast something is moving. Speed ( v ): The measure of how fast something is moving. Distance / Time Distance / Time For example 25 km/h For example 25 km/h or 25 kilometers / per one hour or 25 kilometers / per one hour Units for speed are (m/s) and (km/h) Units for speed are (m/s) and (km/h) 4

5. Differences in words Displacement – how far you got from your starting point – as measured in a straight line. Displacement – how far you got from your starting point – as measured in a straight line. Distance – how far you actually travelled. Distance – how far you actually travelled. 5

6. Instantaneous Speed Instantaneous Speed: The speed at any instance. Instantaneous Speed: The speed at any instance. 6

7. Average Speed Average speed Average speed If we travel 240 kilometers in 4 hours, what is our average speed? If we travel 240 kilometers in 4 hours, what is our average speed? 60 km/h 60 km/h Total distance covered Time interval v = 7

8. Velocity Speed and Velocity are not interchangeable terms. Speed and Velocity are not interchangeable terms. Velocity is speed in a given direction. Velocity is speed in a given direction. A car traveling 60 km/h only expresses speed, but a car traveling 60 km/h going north expresses velocity. A car traveling 60 km/h only expresses speed, but a car traveling 60 km/h going north expresses velocity. 8

9. Constant Velocity Constant Velocity: requires both constant speed and constant direction. Constant Velocity: requires both constant speed and constant direction. In order to have constant direction, the object must be moving in a straight line! In order to have constant direction, the object must be moving in a straight line! 9

10. Changing Velocity Changing Velocity: If either speed or the direction (or both) is changing, then the velocity is changing. Changing Velocity: If either speed or the direction (or both) is changing, then the velocity is changing. You can drive in a circle at constant speed, but your direction is continuously changing. You can drive in a circle at constant speed, but your direction is continuously changing. 10

11. Acceleration Acceleration: The rate @ which velocity is changing. Acceleration: The rate @ which velocity is changing. acceleration acceleration Δ v Δ t a = 11

12. Acceleration In physics, the term acceleration applies to decreases as well as increases in speed. In physics, the term acceleration applies to decreases as well as increases in speed. Typically in a college physics class you would use the term negative acceleration instead of the common term deceleration. Typically in a college physics class you would use the term negative acceleration instead of the common term deceleration. a refers to a Δ in direction as well as a Δ in v. a refers to a Δ in direction as well as a Δ in v. 12

13. Acceleration acceleration = acceleration = Δ v time interval Equation is: 13

14. Acceleration Suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then from 45 to 50 km/h. Suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then from 45 to 50 km/h. What is its acceleration? What is its acceleration? 14

15. Acceleration Answer: We see that the speed increases by 5 km/h during each 1-s interval. Answer: We see that the speed increases by 5 km/h during each 1-s interval. The acceleration is therefore 5 km/h·s during each interval. The acceleration is therefore 5 km/h·s during each interval. 15

16. NEXT TIME…. 16