AP PHYSICS C (Mechanics)
ANALYSIS OF HOOKE’S LAW ORBITAL MOTION DATA
RUN SUMMARY
ANALYSIS BY: ______________
RUN CONFIGURATION
FLIGHT #___ RUN #___
LARGER MASS = _____kg
SMALLER MASS = _____kg
SPRING ID _____
UNSTRETCHED LENGTH = _____m
TARGET ωo = _____RPM
initial distance from axis = _____m
initial distance from axis = _____m
SPRING CONSTANT = _____N/m
VIDEO FILENAME:
AT THE MOMENT OF RELEASE...
ACTUAL ωo = _____ RPM
ACTUAL To = _____ sec
COM is _____ m from the larger mass
INITIAL LENGTH OF SPRING = _____ m
CRITICAL RPM, ωc = _____ RPM. Since the ωo ωc , the masses, when first released, moved
___________.
The initial KEtrans of the larger mass was _____ J, and the initial KEtrans of the smaller mass was _____ J.
The initial elastic PE of the spring was _____ J.
The initial moment of inertia was ___________, and initial angular momentum was _____________.
AT THE MOMENT OF MINIMUM SEPARATION...
SIMULATION
OBSERVED
% difference*
distance of larger mass from COM
distance of smaller mass from COM
minimum separation of masses
length of spring
PEelastic
KEtrans of larger mass
KEtrans of smaller mass
ω
I
L
*Percentage difference of the simulation relative to the observed values.
AT THE MOMENT OF MAXIMUM SEPARATION...
SIMULATION
OBSERVED
% difference*
distance of larger mass from COM
distance of smaller mass from COM
minimum separation of masses
length of spring
PEelastic
KEtrans of larger mass
KEtrans of smaller mass
ω
I
L
*Percentage difference of the simulation relative to the observed values.
PASTE SIMULATION TRAJECTORY PLOT HERE
PASTE VIDEO STILL IMAGE HERE, with points marked
and axes shown, oriented as simulation trajectory plot
is.
PASTE SIMULATION ENERGY PLOT HERE
PASTE TRACKER ENERGY KE of mass A
PASTE TRACKER ENERGY KE of mass B
AP PHYSICS C (Mechanics)
LAB: Hooke’s Law Orbital Motion
NAME:______________________________
Analysis Process
1. Go to the HLOM Data Archive (http://academic.greensboroday.org/~regesterj/data/rgo-HLOM/) and
save the video of your assigned run to a folder on your computer.
2. Start Tracker, open the video, and determine the start frame (when the masses are released) and the
end frame (when either of the masses hits a wall). Fill in that information in the Clip Settings dialog. Also
fill in the frame rate (300 frames/sec) and the step size (5 frames).
3. Fill in the Run Configuration section of the Run Summary.
4. Set the coordinate axes, with the origin at the turntable axis and the x-axis parallel to the massspring-mass system at the moment of release.
5. Set the scale. The rotating apparatus is 0.507 m long.
6. Create a point mass. Rename the point mass appropriately: the 1 kg mass is A, 0.5 kg is B, 0.2
kg is C, and 0.1 kg is D.
7. Set the accurate mass in the mass box on the toolbar. The precise masses are 0.991 kg (A),
0.494 kg (B), 0.196 kg (C), and 0.094 kg (D).
8. Shift-click to mark the positions of the mass throughout the video. Yes, it’s tedious, but do it as carefully as
you can.
9. Repeat steps 6-8 for the other mass.
10. Create a new “center of mass” track.
11. Set the track display so all the mass positions are marked, connected by lines, but
without numbers.
12. DOCUMENT ALL OF THE FOLLOWING CALCULATIONS... Watch the video just prior to the release of the
masses. Determine how many frames it takes the apparatus to turn the last full or half turn, and use that
information to calculate the initial period and initial angular velocity of the system. Fill in these result, as well as
the other items in the At the Moment of Release section of the Run Summary. The “Critical RPM” is the angular
velocity that results in circular motion. To calculate it, set the centripetal force equal to the spring force.
13. Set up the Excel spreadsheet numerical model sim4b.xlsm with the parameters of your run. Cut-n-paste
(or screen snip) the trajectory plot from the simulation, and paste it into the indicated spot of the Run
Summary. Do the same with the trajectory overlay of the video. Rotate the video frame so the x-axis points to
the right. Paste the other indicated plots, from the numerical model as well as Tracker, into the Run Summary.
14. Fill in the Minimum Separation and Maximum Separation sections of the Run Summary. CLEARLY
DOCUMENT ANY AND ALL CALCULATIONS.
FOLLOWUP QUESTIONS
1. Do you think the numerical model did a good job predicting what actually happened? Discuss, including
references to your qualitative impresions as well as specific numerical comparisons.
DELETE THIS LINE & TYPE RESPONSE HERE
2. What happens to the angular velocity of the system as the masses come closer to each other? Explain why,
using physics concepts.
DELETE THIS LINE & TYPE RESPONSE HERE
3. What happens to the kinetic energy of the system as the masses come closer together? Explain why, using
physics concepts.
DELETE THIS LINE & TYPE RESPONSE HERE
4. Describe what happens to the center of mass of the system, and why?
DELETE THIS LINE & TYPE RESPONSE HERE
WHAT TO TURN IN...
Print out this document, including your (typed) responses to the Followup Questions. Use a color printer so the
video screenshots look good. Also include all your calculations. These can be handwritten, but must be neatly
and logically arranged.
Email me your TRK file, as well as this document. Your TRK file should be named FlightXRunY.trk (with X
and Y being your flight and run numbers) and the Word doc should likewise be FlightXRunY.doc.