Honors Physics
Chapter 7
Circular Motion Lab
What does it mean to move in a circle? In this experiment we will explore uniform circular motion (to the best of our
capabilities) with a low – tech apparatus but employ high tech analysis.
Question: For an object swung nearly horizontally, how are force, tangential speed, and radius related?
Hypothesis: _______________________________________________________________________________
Materials List:
1. fishing line
2. 2-hole rubber stopper
5. plastic tube
6. set of masses
3. masking tape/alligator clip
7. Stop watch
8. Excel
4. meter stick
9. e - balance
Background:
Over
Procedure:
6. Next place a hooked mass, M4, that is more than 100. grams but less than
400. grams at the end of the string. Without changing the length, L, or the
position of the alligator clip, repeat step 3. Record M4 and total times.
7. Next place a hooked mass, M5, that is more than 100. grams but less than
500. grams at the end of the string. Without changing the length, L, or the
position of the alligator clip, repeat step 3. Record M5 and total times.
8. Now change the length, L, so that it is between 40 & 50 cm. Measure and
record L6. Place a 100. gram mass , M6, at the end of the string. Repeat step 3.
9. Now change the length, L, so that it is between 50 & 60 cm. Measure and
record L7 . Keep the same mass , M6, at the end of the string. Repeat step 3.
10. Now change the length, L, so that it is between 60 & 70 cm. Measure and
record L8 . Keep the same mass , M6, at the end of the string. Repeat step 3.
11. Now change the length, L, so that it is between 70 & 80 cm. Measure and
record L9 . Keep the same mass , M6, at the end of the string. Repeat step 3.
12. Determine the mass, m, of the spinning mass and clean up.
Over
Moving in Circles Lab Analysis
Calculations and Plots: Show one sample of each type of calculation then place results in a Results Table.
1. For each of your Mh and L values, calculate the frequency of rotation in rpm.
2. Convert your rpm values to radians/sec.
3. Using your data & FBDs, etc, determine angle the fishing line was below the horizontal for each trial.
4. Determine the radius of revolution for each trial.
5. Determine the time for one revolution for each trail.
6. Calculate Mh/L for each trial.
7. Calculate f2 for each trial.
8. Plot Mh /L vs. f2. Determine the LBF and R2.
 4 2  m 
 .
9. Compute 
 g 
10. There are two methods of determining Fc, one in the vertical dimension - Fcv, the other from circular
dynamics, Fcc. Determine each value for each trial.
11. Plot Fcv vs. Fcc. Determine the LBF and R2.
12. Calculate tangential speed/velocity using kinematics (i.e. radius & Δ t)?
13. Plot (w/LBF & R2) Fcv vs. tangential speed.
14. Plot (w/LBF & R2) Fcv vs. tangential speed2.
Questions & Conclusion: - what to do with all these graphs?
1. Under UCM conditions, is it possible to spin the stopper in a plane at right angles to the plastic tube? Explain.
2. Which plots give straight lines? What is the evidence?
3. What does the slope equal (i.e. what data/constants reside in the slope value) in # 8?
4. Compare the slope in # 8 to the computed value in # 9 using % difference. Have the computed value in the
denominator. What can be concluded?
5. What should the slope in # 11 equal? Before proceeding, check with your teacher. Compare the calculated
slope in # 11 to the accepted value from your teacher using % difference. Have the accepted value in the
denominator. What can be concluded?
6. What can be concluded when comparing plot # 13 to # 14?
7. Does the angle below horizontal affect the results? Explain.