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Activity 2

Activity 2. Graphical Displays of Motion. Goals:. Investigate the differences between motion with constant speed and motion with changing speed. Learn to use the simple technology of Dot-Cars to collect motion data.

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Activity 2

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  1. Activity 2 Graphical Displays of Motion

  2. Goals: • Investigate the differences between motion with constant speed and motion with changing speed. • Learn to use the simple technology of Dot-Cars to collect motion data. • Create bar graphs and line plot graphs to illustrate constant speed motion and changing speed motion. • Learn how graphs can be used to understand an objects motion. • Use probe technology and computers to collect and graph motion data.

  3. Average Speed • To find average speed, you divide distance by time • d/t = average speed • For example, if a buggy went a distance of 100cm in 5 seconds, we would divide the distance (100cm) by the time (5 seconds)…. 100 divided by 5 = 20. • Therefore, the average speed of this buggy would be 20cm/s

  4. Constant Speed • When the speed of an object does not increase or decrease, it is moving at a constant speed. • Our red and blue buggies both move at a constant speed, though the red buggy travels at a faster constant speed than the blue buggy. • Using the Dot-Car, we are able to investigate the motion of the red and blue buggies.

  5. Constant Speed Results • When the blue buggy pushed the Dot-Car, the marks left by the Dot-Car looked like this: • The Dot-Car leaves a dot at every time-click and each time-click is exactly the same amount of time. • The dots above tell us that the blue buggy was moving at a constant speed because they are the same distance away from each other from start to finish.

  6. Constant Speed Results • When the red buggy pushed the Dot-Car, the marks left by the Dot-Car looked like this: • The dots above are the same distance apart, so we know that the red buggy was also moving at a constant speed.

  7. Comparing Constant Speed • We can learn more about an object’s motion by looking at the dots left by the Dot-Car. • If a dot-car is moving slow, the dots will look more like dots and they will be closer together. • If the dot-car is moving faster, the dots will look more like dashes and they will be further apart.

  8. Graphing Constant Speed • This bar chart shows what constant speed looks like. • You can tell that it is constant speed because the height of each bar, for each buggy, is the same.

  9. Graphing Constant Speed • This line graph shows what constant speed looks like. • You can determine constant speed on a line graph because the lines are straight. If the lines had curves, it would not be constant speed.

  10. Non-Constant Speed • We can investigate non-constant speed, also known as changing speed, by using the dot-car on a ramp. • If we release the dot car from the top of a ramp that is not too steep, the dot car will slowly increase in speed as it goes down the ramp.

  11. Non-Constant Speed • If we release the dot car from the top of a ramp that is much steeper, the dot car will quickly increase in speed as it goes down the ramp.

  12. Non-Constant Speed • The dot-car on the first ramp will leave a dot trail like this: StartFinish • As the dot car begins down the ramp, a dot can be seen at the beginning. As the dot-car slowly increases in speed, the dots become longer and longer dashes and they gradually get further and further apart. • This shows us speed that is increasing slowly.

  13. Non-Constant Speed • The dot-car that was released from the steeper ramp will leave a dot trail that looks like this: StartFinish • As the dot car begins down the ramp, a dot can be seen at the beginning. However, as the dot-car quickly increases in speed, the dots immediately become longer and longer dashes and they quickly get further and further apart. • This shows us speed that is increasing rapidly.

  14. Graphing Non-Constant Speed • The different heights of the bars in this chart show us non-constant speed. • If it was constant speed, the bars would be the same height. • We can also tell that the dot car moved faster on the steep ramp than the shallow ramp.

  15. Graphing Non-Constant Speed • In this line graph we can see the low ramp’s curve occurs slowly just as the dot-car’s speed increased slowly. • The steep ramp’s curve occurs quickly, just as the dot-car’s speed increased quickly on the steep ramp.

  16. Questions to Think About • How is constant speed different from non-constant speed? How can this difference be displayed graphically? • How can you tell if an object is traveling at a constant speed? ……..speeding up?......slowing down? • How can you illustrate constant speed and changing speed using bar graphs and line graphs? • How can graphs be used to understand the motion of objects?

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