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Distance vs. Time.  Describing a journey made by an object is very boring if you just use words. As with much of science, graphs are more revealing.

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Presentation on theme: "Distance vs. Time.  Describing a journey made by an object is very boring if you just use words. As with much of science, graphs are more revealing."— Presentation transcript:

1 Distance vs. Time

2  Describing a journey made by an object is very boring if you just use words. As with much of science, graphs are more revealing.  Plotting distance against time can tell you a lot about a journey.

3  Let's look at the axes:

4  Time always runs horizontally (the x- axis). The arrow shows the direction of time. The further to the right, the longer time from the start.

5  Distance runs vertically (the y- axis). The higher up the graph we go, the further we are from the start.

6  If something is not moving, a horizontal line is drawn on a distance-time graph.  Time is increasing to the right, but its distance does not change.  This graph shows an object that is stationary.

7  If something is moving at a steady speed, it means we expect the same increase in distance in a given time.  Time is increasing to the right, and distance is increasing steadily with time.

8  This graph shows an object that moves at a steady, constant speed.

9  Both the lines below show that each object moved the same distance, but the steeper yellow line got there before the other one.  What does this indicate?

10  A steeper slope indicates a larger distance moved in a given time. In other words, higher speed. yellow  This is shown in yellow.

11  Yellow 3 m/s  Yellow: speed = distance / time = 30 m / 10 s = 3 m/s  Blue 1 m/s  Blue: speed = distance / time = 20 m / 20 s = 1 m/s

12  For the first part of the journey shown by the graph below, the object moved at a steady (slow) speed.

13  Then the object suddenly increased its speed, covering a much larger distance in the same time.  The speed increased in the second part of the journey.

14  The line below is curving upwards. This shows an increase in speed, since the slope is getting steeper over time.

15  In other words, in a given time, the distance the object moves is larger.  It is accelerating.

16  There are three parts to the journey shown here… Where is the graph showing motion that is:  Stopped?  Moving at a quick constant speed?  Traveling at a slow constant speed? A B C

17  The graph below shows several stages of motion: Stage 1: 100 m in 10 s. Stage 2: Stage 2: 50 m in 10 s. Stage 3: 150 m in 20 s. Calculate the speeds of each stage, indicated by the colors.

18  The graph below shows several stages of motion: Stage 1: speed = distance / time = 100 m / 10 s = 10 m/s Stage 2: 5 m/s Stage 2: speed = distance / time = 50 m / 10 s = 5 m/s Stage 3: speed = distance / time = 150 m / 20 s = 7.5 m/s.

19  The graph below shows several stages of motion: Stage 1: constant speed at a relatively high rate Stage 2: Stage 2: constant speed at a relatively slow rate Stage 3: constant speed at a “medium” rate (between the others)

20  The graph below shows several stages of motion: The slope of the line (its steepness) indicates rate of change of position. Speed can be estimated by the slope of the line… faster, slower, etc.

21  Distance vs. time graphs also indicate the position of the object. Stage 2: Stage 1 & Stage 2: object is moving away from the starting point Stage 3: object is moving back toward the starting point (it comes back to zero)

22  The steeper the line on a distance vs. time graph, the faster the object’s speed.  A curved line indicates a change in speed (accelerating or decelerating).

23  Lines pointing up indicate moving away from the starting location.  Lines pointing down indicate moving back towards the starting location.

24  Let’s see how much this makes sense to you…  This is not for a grade, just to let me know how much of this and what parts of it you “get.”

25  To learn about speed vs. time graphs, visit this link:


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