2. Speed and Velocity Speed and Velocity Chapter 9 sec 2

3. Objectives for today Learn how to calculate speed How to describe the changes in velocity Interpret graphs of distance over time.

4. Calculating speed Speed- the distance an object travels per unit of time. Speed is equal to the distance divided by the amount of time it takes to get there. Speed= distance/ time Speed= distance time *To calculate the speed of an object, divide the distance the object travels by the amount of time it takes to travel that distance.*

5. The speed equation is made up of a unit of distance (meters, centimeters, kilometers) divided by a unit of time (seconds, hours). The slash is said as “Per” -2m/h If I throw this ball 10 meters and it gets there in 2 seconds then we can say that I threw the ball 5 meters per second.

6. Average speed To calculate the average speed divide the total distance traveled (d) by the total time (t). Average speed (v)=d/t Example pg. 343 Answer this: I traveled 13 meters in 5 seconds, then I traveled 25 meters in 10 seconds, what is my average speed?

7. Answer : v=d/t Total Distance = 38m Total time= 15 sec. 38m/15s= 2.5333 m/s = 2.5333 meters per second.

8. If you know any two quantities you can calculate the third D ST

9. Instantaneous speed Instantaneous speed Instantaneous speed- The rate at which an object is moving at a given instant in time. Speed RIGHT NOW!

10. Velocity Velocity is speed in a given direction The velocity of a storm can be described as 25 km/h to the east Velocity can change over time Changes in velocity can be due to changes in speed, changes in direction, or both

11. Examples of Velocity A hurricane is traveling 90 km/h in an eastwardly direction The train is traveling 50 km/h north write your own example of velocity

12. Velocity Velocity- Velocity- speed in a given direction. – Displacement and velocity are VECTORS. – *Changes in velocity may be due to changes in speed, changes in directions, or both*

13. Speed vs. velocity Velocity is a vector, because it has direction. Speed is the magnitude of velocity-- it doesn't have direction Suppose that some object is moving in a circle around some central point at a specific speed. circle The speed does not change, but the velocity vector is always changing.

14. Graphing Speed You can show motion on a line graph in which you plot distance versus time Time is shown on the horizontal axis (x axis) Distance is shown on the vertical axis (y axis) The line is called the slope you can calculate the slope of a line by dividing the rise by the run

15. Graphing Speed Slope- tells you how fast one variable changes in relation to another variable. The slope of a distance-over-time graph represents speed. That is the rate that distance changes in relation to time. The steeper the slope the greater the speed. Constant slope represents constant speed.

16. Time (min) GRAPHING MOTION Distance (m) 07654321 0 200 400 600 800 1000 1200 1400 point (x,y) slope = rise run run = 2 min rise = 400 m

17. The distance traveled by 2 crawling babies is shown in the table. Graph the information and find the slope of each line. What is each baby’s speed? Time (s) Baby Sarah Distance (m) Baby Scott Distance (m) 000 10.50.4 210.8 31.51.2 421.6

19. Finding Your Average Speed You are planning a trip to Las Vegas. The distance between Los Angeles and Las Vegas is 450 km (275 miles). You are going to make at least 4 stops along the way. Determine how long you will travel before you make a stop. At what speed will you be traveling? How long will you stop at each point. What is the total time it took you to get to Vegas? Determine your average speed....now graph your trip!!!

20. timedistance 00 113 225 340 451 566 678