course phy 202
3:20 pm 2/28/10
Experiment kinmodel_03: Equipartition of energy and the direction of disorder to (increasing or decreasing)Observe the first several seconds of the simulation at the 'slow' default speed. You will see how the particles initially are all moving in or very close to the x direction, with little or no y component. Note the x and y kinetic energies, displayed near the top of the screen.
• Observe what happens to the directions of motion of the particles as they start colliding.
• Observe what happens to the x and y kinetic energies.
• Is the system more organized at the beginning of the simulation or after a couple of minutes?
• If the x and y kinetic energies were averaged for 100 years, starting a few minutes after the simulation began, which do you think would be greater?
Run the simulation in this manner several times, and each time determine how long it takes before the total y kinetic energy is first greater than the total x kinetic energy. Report your results.
Now take some data:
• Running at the fastest default speed, stop the simulation with the pause/break key every few seconds, keeping your eyes closed for at least 2 seconds before stopping the motion.
• Write down the x and y kinetic energies each time.
• Do this at least 30 times.
• Find the average of all your x and all your y kinetic energies.
• Do you believe the difference in the averages is significant, in that the direction that has the higher average will always tend to have the higher average every time the simulation is run?
The motion starts to take on more of a y component, that is, the particles start moving in the y direction more.
The x KE starts to decrease as time goes by, and the y KE starts to increase as the x goes down.
It is probably more organized after a few minutes of running.
I would think the y would be a greater average after a hundred years.
I usually takes about 2 seconds before the y KE is greater than the x KE.
DATA_____
Average of 30 trials---X=1425.67
Y=1635.6
There is a 210 difference between the two, so I do think there is a significant difference. I do think the y direction tends to be higher than the x most of the time.
There is in fact no difference in the simulation's results between average x and average y kinetic energies. However it takes a very large set of trials (say, 10 000 or more) to experimentally verify this. On a 30-trial test, it is common that one or the other appears to be greater.
These results actually make a very good basis for a statistical study, but in this course we're not going to get that deep into the statistics.