Be sure to review the data from the staged races. You should have completed one graph with the steady walk, jog, and run plotted on the same graph.
- If the graph line is straight, the speed is constant.
- The slope of a line on a distance vs. time graph is the speed. Speed is the rate of change of position or how fast the position changes. The steeper the slope, the greater the speed. The shallower the slope, the slower the speed.
- Speed is reported in units like meters / second. Graphing distance on the vertical axis of a graph and time on the horizontal is consistent with the mathematics that apply to these motion concepts. (Ask your math teacher for verification>)
- Average speed can be calculated by dividing the distance traveled by the time elapsed. A major learning goal is for you to understand the sense in which this calculation gives the average or mean speed. And how this idea is related to the idea of constant speed.
- As we look at examples where speed changes, we want to bring up the idea of speed at a particular moment or instantaneous speed.
Two quantities are fundamental to examining motion:
- Change in position (distance from start to end)
- Change in time (duration from the beginning of the event to the end)
- When the change in position is divided by the change in time, the results is called average speed. We will discuss what the term “average” means here. It may be a little different from what you think.
- To help us visualize these quantities and how and when they change and also how and when they remain constant, we will learn to construct distance vs. time graphs. The graph is one of the main analytical tools you have available to you in middle school science. We hope you learn how to graph, which graph to use with which questions, and how to interpret graphs.
- Pay close attention to the discussion of the analysis of motion, the meaning of concepts, the mathematical and graphical techniques. YOU MUST ASK QUESTIONS!!! ESPECIALLY IF THERE IS SOMETHING THAT SEEMS CONFUSING.
A little quiz. You will be asked to make sketch graphs or prediction graphs. These do not use actual numbers. You sketch in the graph line you think would apply if you plotted the actual numbers. You may use the paper graph you made for the steady walk, jog, and run. No other references. Put ipads away. Listen closely for the events you are to include on the sketch graph. Take pictures of your predicted graphs. This is a quiz to see if you have been thinking about motion and how motion appears on distance vs. time graphs. It is also a quiz to see how you are thinking about motion and graphing.
After the quiz, make correct graphs for the following:
- On the same paper, the fast to slow and the slow to fast.
- On the same paper, the tortoise and the hare.
- Any other event for which we have data.
- On the back of each paper, explain the graphs and the motions in words.
Graphing guideline that are always useful and appropriate:
Use pencil on hand-drawn graphs. Sharp and dark.
Label axes first with variables and units on the appropriate and customary axis. It should be neat. Everything should be labeled.There should be a title. The title can be a question. The graph should be appropriate to the data and the question under investigation. DO NOT use ink or color until the graph has been checked and is perfect. Graph paper is available at: http://rfrazier.msblogs.aes.ac.in/various-resources/graph-paper/
- It should include all data. Discuss with teacher and other students when there are extreme outliers.
- It should be consistent.
- I should be as big as possible. Whenever it can, the graph should cover at least 1/2 the page.
- It should be convenient. Always base the scale on what 1 division on the graph paper will equal. Do not choose based on how many divisions equal 1 unit of the variable. Pay close attention to the recommended series of possible scale factors. These always work.