Exponential functions appear in many situations in ordinary life. For this activity, you will gather some data about how well a paper towel absorbs water and use that data to create a graph and a best-fit function.
1. Cut a strip a paper towel about 1 centimeter wide and at least 12 centimeters long. Use a ruler to mark off and number centimeters on the paper towel strip.
2. Put a little water in a plastic cup. You will only need enough to cover the bottom of the cup. Do not fill it more than 1 centimeter deep.
3. One of you will serve as a timer. The other will handle and observe the paper towel. The observer will watch the paper towel and call out when the water reaches each centimeter mark. The timer will watch the clock and record data.
4. When the timer is ready to begin, the observer will lower the paper towel so that it just touches the water in the cup. Be ready because the water will rise very quickly initially! You may fold the top of the paper towel over the edge of the cup to hold it in place.
5. Record the following data:
6. Enter your data into your graphing calculator, plot the data on a graph, and find the best fit exponential function:
y = a * bx