Making and Interpreting Distance – Time Graphs Graphing Speed Making and Interpreting Distance – Time Graphs

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

CONSTANT SPEED If something is “constant” what does that mean? It does not change So… what does the term constant speed mean? Speed that does not change is constant speed. Name some things that you think have constant speed. Think outside the

GRAPHING CONSTANT SPEED DISTANCE-TIME GRAPHS straight diagonal line t d 100 90 80 70 60 50 40 30 20 10 1 2 3 4 5 20 40 60 80 100 D I S T A N C E (m) 0 1 2 3 4 5 TIME (sec) Describe the shape of the line for constant speed

GRAPHING CONSTANT SPEED DISTANCE-TIME GRAPHS A has the > slope therefore it has the > constant speed. How do you know? A B C t d 100 90 80 70 60 50 40 30 20 10 1 2 3 4 5 20 40 60 80 100 D I S T A N C E (m) 0 1 2 3 4 5 TIME (sec) Which object has the greatest constant speed?

GRAPHING AVERAGE SPEED DISTANCE-TIME GRAPHS A flat horizontal line means motion stopped. What does this part of the line mean? 100 90 80 70 60 50 40 30 20 10 t d 1 2 3 4 5 10 30 40 80 D I S T A N C E (m) 0 1 2 3 4 5 zigzag TIME (sec) Describe the shape of the line for average speed?

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.

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.

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

CURVED GRAPHING ACCELERTION DISTANCE-TIME GRAPHS 100 90 80 70 60 50 40 30 20 10 t d 1 2 3 4 5 10 20 40 70 110 D I S T A N C E (m) CURVED 0 1 2 3 4 5 TIME (sec) Describe the shape of a line showing acceleration.

INTERPRETING a c b d DISTANCE-TIME GRAPHS TIME (hr) SNAIL RACES MHS INTERPRETING DISTANCE-TIME GRAPHS SNAIL RACES Results a c 100 90 80 70 60 50 40 30 20 10 b D I S T A N C E (in) d Pass out question sheet for this slide. 0 1 2 3 4 5 TIME (hr)

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

Model Car Race Results Graphed I S T A N C E (m) TIME (sec) Your graph should look like this.

A few questions for you: What does the horizontal line for car C indicate? Which car(s) is/are accelerating? How do you know? Which car(s) is/are traveling at constant speed? Which car won the race? How do you know which car won the race? What is the average speed of each car in the race? It had to stop during a portion of the race Car D because its line is curving. Cars A and B show straight diagonal lines Car D because it traveled farther in the 10 seconds Because it traveled farther in the 10 seconds A 3 m/s B 2 m/s C 2.5 m/s D 3.6 m/s

QUIZ 1.The graph used to graph speed is called a ___________-______ 2. Speed that does not change is called ____________ speed. 3. Speed that fluctuates is called _______________ speed. 4. The shape of a line on a distance-time graph for constant speed is a ________________, _______________ line. 5. The > the slope the _______ the constant speed. 6. On a distance time graph a line that is horizontal indicates ___________________ ______________. 7. The formula for calculating speed is _________=__________ 8. Speed in a given direction is called _________________. 9. The rate of change in velocity is called___________________.

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