Name ______________________________________ Date _____________________ Period ___________
Falling coffee filters
Background Information: The amount of air resistance an object encounters is
directly proportional to its surface area and velocity. Terminal velocity, vt, is
achieved when the air resistance equals the object's weight and the object can
no longer accelerate. It reaches a state of dynamic equilibrium.
Materials:
Each group needs three members: holder, measurer, recorder. Each group
needs three stacks of filters (1 filter, 2 filters, 4 filters) and two meter sticks.
The purpose of the lab is to discover the release height for each group of filters
that will enable two groups, which have reached terminal velocity, to reach the
floor at the same time.
Experimental Procedure/Data
2 filters
Holder: Experiment with simultaneously releasing the groups containing 1 filter
and 2 filters to determine a best estimate for the appropriate release heights that
allow the two groups to strike the ground simultaneously. When ready, hold each
group steady so that their distance above the ground can be measured. Make
sure that the flat side is facing the ground.
Measurer: Measure the mass of each group of filters. Do NOT multiply the total
by the mass of one filter - MEASURE each group and record your information in
the data table provided below. Then measure how high each group of filters is
above the ground just as they are released. ALL filters should be released AT
OR ABOVE 1.5 meter. Record to the nearest 1.0 cm.
Recorder: Record your heights in Data Chart #1. Repeat two more times. If all
trials seem equivalent, calculate an average value.
4 filters
Holder: Experiment with simultaneously releasing the groups containing 2 filters
and 4 filters to determine a best estimate for the appropriate release heights that
allow the two groups to strike the ground simultaneously. When ready, hold each
group steady so that their distance above the ground can be measured. Make
sure that the flat side is facing the ground.
Measurer: Measure the mass of each group of filters. Do NOT multiply the total
by the mass of one filter - MEASURE each group and record your information in
Name ______________________________________ Date _____________________ Period ___________
the data table provided below. Then measure how high each group of filters is
above the ground just as they are released. ALL filters should be released AT
OR ABOVE 1.5 meter. Record to the nearest 1.0 cm.
Recorder: Record your heights in Data Chart #1. Repeat two more times. Input
the best trial's results in the final column. If all trials seem equivalent, calculate an
average value.
Data Table III: Mass Data
Measurer: Measure the mass of each group of filters. Do NOT multiply the total
by the mass of one filter - MEASURE each group and record your information in
the data table provided below.
Name ______________________________________ Date _____________________ Period ___________
Falling coffee filters
Data Table I: 1 & 2 filter
Trial 1 height
(m)
Trial 2 height (m)
Trial 3 height
(m)
Average
height (m)
1 filter
2 filters
Time to fall _____________
Terminal velocity (1 filter) __________________ Terminal velocity (2 filter) __________________
Data Table II: 2 & 4 filters
Trial 1 height
(m)
Trial 2 height
(m)
Trial 3 height
(m)
Average
height (m)
2 filter
4 filters
Time to fall _____________
Terminal velocity (2 filter) __________________ Terminal velocity (4 filter) __________________
Mass Data:
Number of filters
1
Mass (g)
2
4
Draw 3 free body diagrams
1. when first released, v = 0
2. after falling a short time, v is small
3. after reaching terminal velocity v = vt
Name ______________________________________ Date _____________________ Period ___________
Questions:
What familiar device uses terminal velocity as a principle?
How could you reduce the rate at which the coffee filters fell?
Design a device out of coffee filters that would carry three washers and descend at the
slowest speed.
Conclusions (Analyzing and Interpreting Results)
Starter Phrases for Conclusions
1. Topic sentence (purpose)
• In this investigation we were trying to find if …
2. Summarize results (patterns, trends with supporting data)
• We found that … (be sure to use specific data to support your claim
3. Make logical inferences (think about why things happened the way they
did)
• One reason we may have gotten these results is because …
4. Discuss limitations
• Some problems that may have affected our results include …
• In order to get better results …
5. Further questions
• A new, related question that I might be able to answer with an experiment
is …