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.

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.

Review 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.

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.

I count 6 …. 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? Changes direction? 5 1 Speeds up 2 ??? Speeds up 4 Is there any other place that its velocity will change? 3 Slowing down is also considered to be acceleration. 6 I count 6 …. Let’s look at why this might be.

Formula for CALCULATING ACCELERATION final velocity - original velocity time for change to occur acc = Vf - Vo acc = 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? Vf_-_Vo acc = t 40 m/s__-__20 m/s acc = 4 sec acc = 5 m/s/s

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? Vf__- Vo t acc = 20 m/s_-_40 m/s 5 seconds acc = Notice that the answer is a negative number. This indicates that the roller coaster slows down. acc = - 4 m/s/s Negative acceleration is also known as __________________. deceleration

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.

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

FIRST ANNUAL D C B A SHMS Snail Races

INTERPRETING a c b d DISTANCE-TIME GRAPHS TIME (hr) SNAIL RACES SHMS 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 similar to this.

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