Union College
Winter 2015
Physics 120 Lab 6: A study of Air Resistance
The Experiment:
By timing (with stop watches) the fall for 4 different size packets of coffee filters to drop down the
stairwell, determine the terminal velocity and force of air resistance in each case.
Note: the coffee filters should be handled carefully to avoid changing their cross-sectional area. To make
the groups of filters, only gently page through an edge.
Use your ingenuity to measure the height of the drop.
Suggestions for getting good results:
1. The time measurements need to be reliable to tenths of a second. There is a potential source of
systematic source of error due to the person doing the timing being a distance from either the place where
the coffee filter is released or where it hits the floor.
2. Make sure to get enough data to yield reliable determinations of each packet’s velocity.
Analysis:
Use Excel to make a plot with log(Fair) on the y-axis and log(vel) on the x-axis. Fit a straight line, and
note the slope. If the fit is good, the relationship is a simple power law, and the slope is the power of vel.
in the relationship.
Do the following instructions in Excel to perform a regression analysis to obtain the uncertainty in the
slope: Under the “data” menu, select “data analysis,” select the columns of data for the x and y axis data.
In the new chart that appears, the slope, y-intercept, and their uncertainties are the four numbers in the
lower left corner.
Your Report:
Submit an abstract, the initial handout with your answers written in the spaces, and your Excel data
table and graph. Be sure to state your inferred equation relating the Force of air resistance and velocity,
and be sure to state the uncertainty in the power of velocity.