Duck Lab
clamp
1. Obtain a 1 meter length of string, a rubber stopper,
Mass hanger
timer, ruler and mass hanger.
2. Separate yourselves from the other groups.
3. Spin the rubber stopper in a flat, horizontal circle over your head at a constant
speed.
4. Determine the period of the rubber stopper. Show your calculation in your lab
notebook.
5. Determine the circumference of the stopper’s path. Show your calculation in
your lab notebook.
6. Calculate the stopper’s linear speed. Show your calculation in your lab
notebook.
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7. Now repeat the above but attach the 50 g mass hanger to the other end of the
string, the part hanging below the plastic tube, and spin the stopper at a speed
that will allow the hanger to be suspended.
 Was the speed required for the above action specific or would any
speed have allowed you to perform the task?
8. Let us now look for some connections.
 Measure a length of 0.7m from the end of the rubber stopper along the
string to the top of the tube. Move the clamp along the string until it just
touches the tube with the measured length. Place mass hanger on the loop
of the string, add mass to the hanger until there is 80 g on the hanger. Hold
the apparatus according to the diagram and spin the stopper in a horizontal
circle and keep the length of the string from changing.
9. Could you spin the stopper at any speed and have the length of the string stay
the same?
10. Was the speed you spun the stopper at a specific amount?
Duck Lab
11. Determine the speed the stopper was traveling at while rotating. Use your
knowledge of circular motion, ruler and stopwatch to calculate the speed of the
stopper. Write your methods and data into your lab notebook.
12.Increase the hanging mass by 20 g. Spin the stopper again. Did you have to
increase or decrease the speed you spun the stopper at? Use the same method
you used before to determine how fast the stopper was spinning.
13.Add another 20 g to the hanging mass and determine how fast you needed to
spin the stopper. Compare each of your speeds for 80g, 100g and 120g graphing
the data if needed to help see any relationships. What type of pattern do you
observe? If necessary, repeat for more data points with different amounts of
mass hanging from the string. Remember to only spin the stopper fast enough
to keep the hanging mass supported, not falling or attempting to be shoved into
the tube.
a. What do we call a change in motion? ______________________
b. In general, what causes changes to an object’s motion? __________________
(Hint: Think about Newton’s 2nd law)
c. When you spin it, what object is causing the stopper to change its motion?
Draw a FBD for the stopper.
Draw a FBD for the hanging mass
What force is causing the stopper to rotate? What is this force equal to?
d. In what direction is the force acting? ___________________
e. What do we call this force? ___________________________________
f. What direction is the acceleration resulting from this force?
g. Is the acceleration caused by a Net Force? Explain your reasoning?
h. As the hanging mass was increased, what happened to the speed of the spinning
stopper? What is the relationship between the Net Force and the speed of the
stopper? Think about what the relationship may be, base your decision on your
textbook reading assignment.
Make a graph of Fnet vs speed using your collected data. What is the
pattern as shown by the graph? Is the pattern a linear or not linear relationship?