Terminal Velocity Lab
Honors Physics
Galileo tried to prove that all falling objects accelerate downward at the same rate. Falling objects do accelerate
downward at the same rate in a vacuum. Air resistance, however, can cause objects to fall at different rates in air.
Air resistance enables a skydiver’s parachute to slow his or her fall. Because of air resistance, falling objects can
reach a maximum velocity or terminal velocity. In this experiment, you will study the velocities of two different
falling objects and the effects of surface area & mass on the terminal velocity.
OBJECTIVES
In this experiment, you will
• Use a computer-interfaced Motion Detector to measure distance and velocity.
• Produce distance vs. time and velocity vs. time graphs.
• Analyze and explain the results.
motion detector
MATERIALS
computer,
right-angle clamp
Vernier LabPro
basket coffee filter
Vernier Motion Detector
book
Logger Pro
meter stick
masking tape
metal rod
Lab Pro
Set-up:. (see Figure 1)
Set up the equipment as shown. Connect the motion sensor to the lab pro using the gray cable and the lab pro
to the computer using the USB cable. Be careful to make sure the motion detector is clear of the desk and there
are no cables hanging in front of the motion sensor. To open the data file, open internet explorer and type
“physics” in the address bar. Click on the Honors Physics 11 directory and open the file named “Terminal
Velocity Lab Data File”.
Part A: Comparing Terminal Velocity of a coffee filter to a book
1. Hold a basket coffee filter with the open side facing up at a position 0.5 m from (at the 0.5m mark on the
ring stand) and directly below the Motion Detector. Click to begin data collection. When you hear sound
coming from the Motion Detector, allow the coffee filter to drop straight down. If you do not get a good
graph of the coffee filter falling completely to the ground, perform the experiment again until you get an
acceptable graph.
2. Store the data by selecting “Store Latest Run” from the experiment menu. This will move the graphs into the
background which will let us perform another experiment without losing the data from the coffee filter.
3. Perform the experiment again using the book instead of the coffee filter. If you do not get a good graph of
the book, repeat the data taking procedure until you have an acceptable graph.
4. Autoscale each graph.
5. Examine the velocity graph to find the maximum velocity of the coffee filter and book while falling to the
floor. This can be done by clicking on the examine button,
velocity. Record these values in the data table.
, and moving the cursor to the maximum
6. Print the Graphs for your lab report.
7. Save the data file to your student drive in case you need the data when answering the questions.
Coffee Filter
Book
Maximum Velocity = ____________
Maximum Velocity = ____________
Part B: Effects of Surface Area
In order to examine the effects of surface area on terminal velocity, we will drop the coffee filters and find the
terminal velocity. To change the surface area, we can fold the coffee filters. This will keep the same mass while we
change the surface area as the filter falls to the ground.
Procedure
1. Clear all the data from the previous experiments.
2. Drop the coffee filter as done in the previous part of the experiment. Again, if you do not get a good graph of
the data, repeat the data collection until you get one that is acceptable.
3. Cut the unnecessary data from the graphs. This can be done by selecting the data to be removed and pressing
the “ALT –“
4. Autoscale each graph.
5. Save the file for the whole coffee filter.
6. Fold the coffee filter in half and repeat the data collection. Cut the unnecessary data from the graphs, autoscale
the graphs, and save the file.
7. Fold the coffee filter again so that one fourth of the surface area is showing while it falls to the floor. Again
cut the unnecessary data, autoscale the graphs, and save the file.
8. Fold the coffee filter one more time so that one eighth of the surface area is showing. Repeat the data
collection and save the data file.
Analyzing the data
In order to find the find the terminal velocity as the coffee filter fell to the ground we need to examine the velocitytime graph. The coffee filter will be at terminal velocity when the velocity is relatively constant. We want to find
the average velocity during this time. Start by highlighting the area of the velocity graph where the filter is at
terminal velocity. Click the
button to display the statistics of that region of the graph. The mean in the
statistics window will give us the average velocity during the highlighted region. Use this value as the terminal
velocity.
Repeat this procedure for the other trial and record the terminal velocities in the data table below.
# of Folds
0
1
2
3
Terminal Velocity
Part C: Effects of mass
In order to examine the effects of mass on the terminal velocity, we will drop multiple coffee filters and find the
terminal velocity as they fall to the ground. The data collection and analysis for this part is identical to that done in
Part B. Instead of folding the coffee filter, we will stack multiple coffee filters. This will allow us to examine the
effects of mass while keeping the exposed surface area constant. Find the terminal velocities for 2, 4, 6, 8, and 10
coffee filters. Note that you will not have to take the data for 1 coffee filter because you found that terminal
velocity in Part B. Record your results below.
# of Coffee Filters
Terminal Velocity
2
4
6
8
10
Questions (to be answered in your lab report)
1. How is the position vs. time graphs for the coffee filter different from the graph of the book? Explain the
differences.
2. How is the velocity vs. time graphs for the coffee filter different from the graph of the book? Explain the
differences.
3. In Part A, did either of your objects reach terminal velocity? If so, which one? How do you know?
4. What effect, it any, does the surface area of a falling object have on the terminal velocity? Explain.
5. What effect, it any, does the mass of a falling object have on the terminal velocity? Explain.
6. Draw a free body diagram of the coffee filter as it is falling to the floor at the specified time: A) At the instant
the coffee filter is released. B) Before it reached terminal velocity. C) After it reached terminal velocity.
7. Describe the acceleration graph of an object that is approaching terminal velocity. Explain your graph in terms
of Newton’s 2nd Law.