For this lab, we are going to investigate what the relationship of the amount of air in a balloon and the circumference. You will be working in groups of two. Put a check mark by each step of the experiment as you complete the step. This lab is worth 30 points and must be completed by the beginning of the next class period.
 

• You will need the following materials:

1 meter stick
1 balloon
1 piece of string
hot air
1 colored pencil
1 ruler
1 piece of spaghetti
 
• Experiment setup: You are going to blow one breath of air into the balloon and using the string measure the circumference of the balloon. Use the meter stick to measure the length of string in cm.

 
• Using a normal breath of air, take as many measurements as you can without breaking the balloon and record them into the data table below. Neatly graph your data on the grid below following the directions in Step 4.

DATA TABLE

BREATHS OF AIR	CIRCUMFERENCE (CM)
_	_
_	_
_	_
_	_
_	_
_	_
_	_
_	_

• Your graph is to have the following requirements.
• Set up your graph with the number of breaths on the x axis and the circumference on the y axis.
• Choose an appropriate scale for both the x and y axes.
• Label each axis
• Put a title on your graph
• Graph the data
• Place your piece of spaghetti on the data points so that it goes through as many points as possible. If it does not go through the points, make sure that there are the same number of points above the spaghetti as below. Make a line with your colored pencil and ruler where the spaghetti falls. Make sure to put arrows on the ends of the line.

 
• Get a graphing calculator
• Press STAT and ENTER and clear L1 and L2
• Enter your data into L1 and L2
• Turn your STATPLOTS on by pressing 2nd, Y=, ENTER and highlighting ON
• Make the Xlist: L1 and the Ylist: L2
• Choose an appropriate WINDOW and enter your values for the window in the box provided:


• Press GRAPH
• · To find the 'rule' for your data, press STAT, arrow to the right once and press the number by LinReg and ENTER
• Record the rule in the space provided: y= _______________________________________
• Go to Y= and enter the equation into the Y1=.

 
• Neatly write your rule to the right of your graph.

 
1. Is your equation linear, why or why not? Is your equation proportional, why or why not?

 

 
 
 

2. As you put in each breath, on average, how much does the circumference change? Show your work in the space provided.

 

 
 
 

3. If your balloon could keep on expanding, what would be the circumference of your balloon with 15 breaths of air? Show your calculations and write a paragraph explaining how you found your answer.

 

 
 

Using the graph of your equation, if the circumference of the balloon is 65 cm, how many breaths of air did it take? Explain how you got your answer.