2. Graphing Speed Making and Interpreting Distance – Time Graphs

3. GRAPHING SPEED DISTANCE-TIME GRAPHS D I S T A N C E TIME Distance is plotted on the vertical axis. Time is plotted on the horizontal axis.

4. CONSTANT SPEED So… what does the term constant speed mean? If something is “constant” what does that mean? It does not change Speed that does not change is constant speed.

5. GRAPHING CONSTANT SPEED DISTANCE-TIME GRAPHS D I S T A N C E (m) TIME (sec) 012345012345 100 90 80 70 60 50 40 30 20 10 t d 1 2 3 4 5 20 40 60 80 100 Describe the shape of the line for constant speed straight diagonal line

6. GRAPHING CONSTANT SPEED DISTANCE-TIME GRAPHS D I S T A N C E (m) TIME (sec) 012345012345 100 90 80 70 60 50 40 30 20 10 t d 1 2 3 4 5 20 40 60 80 100 Which object has the greatest constant speed? A B C A has the > slope therefore it has the > constant speed. How do you know?

7. GRAPHING AVERAGE SPEED DISTANCE-TIME GRAPHS D I S T A N C E (m) TIME (sec) 012345012345 100 90 80 70 60 50 40 30 20 10 t d 1 2 3 4 5 10 30 40 40 80 Describe the shape of the line for average speed? zigzag What does this part of the line mean? A flat horizontal line means motion stopped.

8. Average Speed Average speed is speed that changes or fluctuates. Most moving objects travel at average speed, they start from a stand still, begin slowly, increase their speed, slow down, speed up, and eventually slow to a stop. On a distance-time graph average speed would appear as a line that changes direction as it goes across the graph. It would be described as a zig-zag line. A slanted line indicates that motion is occurring. A flat horizontal line indicates that motion has stopped but time continues.

9. You will recall from a previous lesson that Speed is calculated using the formula s = d / t What is the average speed of a 18 wheeler driver who drives non-stop 1600 miles from Houston to Los Angeles in 23 hours? S = d / t S = 1600 mi / 23 hrs. S = 69.565 m/hr. Review

10. Acceleration In order to understand acceleration you must understand the difference in speed and velocity. Speed is how long it takes a moving object to travel a distance. Velocity is speed in a given direction. NOW, ACCELERATION IS THE RATE OF CHANGE IN VELOCITY. You must understand that if either speed or direction changes, the object has undergone acceleration.

11. In this diagram, how many times will the people experience acceleration from where they are now to the end of the ride? 1 2 Is there any other place that its velocity will change? Speeds up ??? Slowing down is also considered to be acceleration. I count 6 …. Let’s look at why this might be. Changes direction? 3 4 5 6

12. Formula for CALCULATING ACCELERATION acc = final velocity - original velocity time for change to occur acc = V f - V o t At the top of the hill the roller coaster is moving 20 m/sec and increases in speed to 40 m/sec at the bottom of the hill. It takes 4 seconds to reach the bottom of the hill. What is the roller’s coaster’s acceleration? acc = V f_-_ V o t acc = 40 m/s__-__20 m/s 4 sec acc = 5 m/s/s

13. As it goes up the hill, it slows to 20 m/sec. The total time from the bottom of the hill to the top of the next hill is 5 seconds. What is the acceleration of the roller coaster? acc = V f__ - V o t acc = 20 m/s_-_40 m/s 5 seconds acc = - 4 m/s/s Notice that the answer is a negative number. This indicates that the roller coaster slows down. Negative acceleration is also known as __________________. deceleration

14. GRAPHING ACCELERTION DISTANCE-TIME GRAPHS D I S T A N C E (m) TIME (sec) 012345012345 100 90 80 70 60 50 40 30 20 10 t d 1 2 3 4 5 10 20 40 70 110 Describe the shape of a line showing acceleration.

15. Graphing is something that you must learn how to do in order to be able to pass TAKS ! Let’s check out the First Annual SHMS Snail Race results to see if you can interpret a distance time graph.

17. INTERPRETING DISTANCE-TIME GRAPHS D I S T A N C E (in) TIME (hr) 012345012345 100 90 80 70 60 50 40 30 20 10 a b c d Pass out question sheet for this slide.

18. (sec) (sec) A B C D 0 0 0 0 0 1 3 2 4.25.25 2 6 4 8.5.5 3 9 6 12 12 1 4 8 16 16 3 5 15 15 10 10 16 16 6 6 18 18 12 12 16 16 10 10 7 21 21 14 14 16 16 15 15 8 24 24 16 16 19 19 21 21 9 27 27 18 18 22 22 28 28 10 10 30 30 20 20 25 25 36 36 TimeTotal distance covered (meters) Construct a distance – time graph for the values in the data table. PASS OUT GRAPH PAPER FOR THIS EXERCISE. NEATNESS COUNTS !

19. D I S T A N C E (m) TIME (sec) Your graph should look similar to this.

20. We hope that you have been able to learn something from us. The End