Diving Deeper on Graphing

http://edweb.sdsu.edu/edtec596/Units/Dive/boyles1.html

by

Mark Sovitsky

Introduction

You've had some experience with lines and graphs and yesterday you learned how atmospheric pressure differs at different depths. Today, we're going to learn how that information affects the diver's planning for a dive and why it is emphatically said "Never hold your breath!"

The Task

You will be creating another graph today similar to the one you created yesterday, except that it will look a little different. It won't necessarily be linear. You will, just as you did yesterday, answer the questions posed in the task section and turn them in.

Resources

Resources needed will be at least one computer, some graph paper, rulers.

The Process

  1. Form into your groups from yesterday.
  2. Find your computer and click here to go to our site today.
  3. Read the entire document and print several copies if necessary and answer the following question:
    • What is Boyle's Law?
  4. Set up your coordinate axes and choose the two quantities. Since we're mainly studying pressure and volume, it makes sense that these two will take part.
  5. Re-read the example and plot the points given, ie for 1 ATM, 2 ATM, 3 ATM, 4 ATM, and 5 ATM. Remember that we are dealing with ABSOLUTE pressure, not GAUGE pressure. If you don't remember the difference, talk to your group or click here to find out.
    • Does this relationship look like it's linear (in a line)?
    • What size would you expect at 10 ATM? At 15 ATM?
    • What happens to the balloon at 1/2 ATM? At 1/3 ATM? At 1/4 ATM?
  6. Let's relate it back to y's and x's. Mr. Sovitsky's Law: y is inversely proportional to x. So if x=1 then y=1/1. If x=2 then y=1/2. If x=3 then y=1/3 and if x=4 then y=1/4.
    • Can you guess the function I'm using?
  7. Graph it and note the similarity between the two graphs.
    • If x=100, then what is y?

Evaluation

Students will turn in the two graphs they've created and the answers to the questions in the Task section. Each graph is worth 10 points and each question is worth 2 points.

Conclusion

In this unit, we've continually referred to 1 ATM and greater pressures, but our graphs all start with 0 ATM at 0 feet.