YOUR NAME HERE
DATE
Centripetal Motion Lab
Purpose:
To experimentally determine the relationship between centripetal force, mass, and distance for
an object in uniform circular motion, and compare the experimental data with the theoretical
prediction.
Materials:
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One glass tube
1.50 m of string
6 Heavy Metal
Washers
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Rubber Stoppers,
Sizes # 3,5,6,7,8
stopwatch
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small piece of yellow
tape
meter stick
Procedure A: Force versus velocity
1. In this procedure, we manipulated the centripetal force Fc (represented by the washers). The
mass of the object m (the stopper) and the radius r were constant. The responding variable is
the velocity, calculated from a measurement of Period T and Circumference (2r)
2. We assumed all of the heavy washers have the same mass, and used 2, 3, 4, 5, and 6 washers
in this procedure. Calculate the centripetal force that each of these numbers of washers will
confer to the mass, and record the values in the data table in Newtons. (Use Fg = mg)
3. We repeated this procedure A, each time adding another heavy washer to the end of the tube
to increase the centripetal force, until we reached a total of six washers.
Procedure B: Mass versus velocity
1. In this procedure, we manipulated the mass of the object m. The centripetal force Fc
(represented by the washers) and the radius r will be held constant. The responding variable
is still the velocity, calculated from a measurement of Period T and Circumference (2r)
2. We measured and recorded the masses of each of the stoppers we will use: (#s 3, 5, 6, 7, 8.)
We used the same number of washers (3) for all trials, and the same 0.200 m radius (20cm).
3. We repeated the experiment for each stopper (3, 5, 6, 7, 8) at the top of the string.
Procedure C: Radius versus velocity
1. In this procedure, we manipulated the radius r the radius is allowed to be the following
values: 20 cm; 40 cm; 60 cm; 80 cm; 100 cm. The centripetal force Fc (represented by the
washers) and the mass of the object m will be held constant. The responding variable is still
the velocity, calculated from a measurement of Period T and Circumference (2r)
2. We attached 3 heavy washers to the bottom of the line and one # 5 stopper to the top.
Analysis:
1. Download the Excel Spreadsheet for the lab and enter all of your data.
2. Add a column to the excel spreadsheet that shows the mathematically predicted values (not
experimental values) for the velocities in each case.
3. Use the Excel spreadsheet on the website to make graphs for each procedure. (3 graphs)
a. Use “v” as the y-axis (‘responding’ or ‘dependent’ variable) for each graph.
b. Use “F”, “m”, and “r” as the x-axis (‘manipulated’ or ‘independent’ variables) for each
graph.
c. On each graph, make one line (“data series”) that shows the experimental values, and
one line (“data series”) that shows the predicted values. Make sure each line is
labeled and the two are clearly visible for comparison.
4. Insert each graph and the corresponding data table for each procedure into this section.
Conclusions:
Type a short paragraph that refers to the purpose of the lab. Insert your written conclusion
here. Be sure to address these points:
1. How closely do these graphs help support the formula F = mv2/r? Does the experimental data
match the theoretical prediction?
2. What were the most significant potential sources for error in this experiment?
3. What does the shape of each graph tell you about the relationship between each of the
variables and the velocity? Use at least one full sentence to describe each (3) relationship.
(For example, which are directly proportional? Which are inversely proportional?)