#$&*
course
September 23, 2012 @ 6:22 PM
You should set the system up and allow the pearl to bounce off the bracket a few times. The bracket should be stationary; the pendulum is simply pulled back and released to bounce against the bracket.
Note whether the pearl strikes the bracket more and more frequently or less and less frequently with each bounce.
If the pearl does not bounce off the bracket several times after being released, it might be because the copper wire below the pearl is getting in the way.
If necessary you can clip some of the excess wire (being careful to leave enough to keep the bead from falling through).
If the bracket is tilted back a bit, as shown in the next figure below, the pearl will naturally rest against the bracket. Tilt the bracket back a little bit and, keeping the bracket stationary, release the pendulum.
Listen to the rhythm of the sounds made by the ball striking the bracket.
Do the sounds get closer together or further apart, or does the rhythm remain steady? I.e., does the rhythm get faster or slower, or does it remain constant?
Repeat a few times if necessary until you are sure of your answer.
Insert your answer into the space below, and give a good description of what you heard.
Your response (start in the next line):
The sound or ball & bracket get closer together at a fast pace.
#$&*
If the bracket is tilted forward a bit, as shown in the figure below, the pearl will naturally hang away from the bracket. Tilt the bracket forward a little bit (not as much as shown in the figure, but enough that the pearl definitely hangs away from the bracket). Keep the bracket stationary and release the pendulum. Note whether the pearl strikes the bracket more and more frequently or less and less frequently with each bounce.
Again listen to the rhythm of the sounds made by the ball striking the bracket.
Do the sounds get closer together or further apart, or does the rhythm remain steady? I.e., does the rhythm get faster or slower, or does it remain constant?
Repeat a few times if necessary until you are sure of your answer.
Insert your answer into the box below, and give a good description of what you heard.
Your response (start in the next line):
The sound of this one remains steady after the ball is let go but it does get close together after a few seconds.
#$&*
If the bracket is placed on a perfectly level surface, the pearl will hang straight down, just barely touching the bracket. However most surfaces on which you might place the bracket aren't perfectly level. Place the bracket on a smooth surface and if necessary tilt it a bit by placing a shim (for a shim you could for example use a thin coin, though on most surfaces you wouldn't need anything this thick; for a thinner shim you could use a tightly folded piece of paper) beneath one end or the other, adjusting the position and/or the thickness of the shim until the hanging pearl just barely touches the bracket. Pull the pearl back then release it.
If the rhythm of the pearl bouncing off the bracket speeds up or slows down, adjust the level of the bracket, either tilting it a bit forward or a bit backward, until the rhythm becomes steady.
Describe the process you used to make the rhythm steady, and describe just how steady the rhythm was, and how many times the pendulum hit the bracket..
Your response (start in the next line):
What I did to make the rhythm steady is I took a piece of paper and folded it until it was pretty thick and took a set of book markers (the ones that stick) and put it at the end of the bracket and I then I either slide it closer to the pearl or the end until I got it to barely touch the bracket.
The rhythm of the pearl is quite steady because after a seconds the pearl is hitting the bracket but it is constantly doing it a steady pace and not a fast or slow pace to a complete stop.
The pendulum hit the bracket 21 times until it made a complete stop.
#$&*
On a reasonably level surface, place one domino under each of the top left and right corners of your closed textbook, with the front cover upward. Place the bracket pendulum on the middle of the book, with the base of the bracket parallel to one of the sides of the book. Release the pendulum and observe whether the sounds get further apart or closer together. Note the orientation of the bracket and whether the sounds get further apart or closer together.
Now rotate the base of the bracket 45 degrees counterclockwise and repeat, being sure to note the orientation of the bracket and the progression of the sounds.
Rotate another 45 degrees and repeat.
Continue until you have rotated the bracket back to its original position.
Report your results in such a way that another student could read them and duplicate your experiment exactly. Try to report neither more nor less information than necessary to accomplish this goal. Use a new line to report the results of each new rotation.
Your response (start in the next line):
When the bracket is parallel to the side of the book the pendulum gets closer to the bracket at a pretty good steady rhythm
When the bracket is moved counter-clockwise at 45 degrees the pendulum is steady in the beginning then when it gets closer and closer to the bracket it is going at a faster pace than before.
When the bracket is moved counter-clockwise at another 45 degrees the pendulum is the steam, steady in the beginning then when it gets closer and closer to the bracket it is going at a fast pace.
As I continued to move 45 degree counter-clockwise movements I noticed that it was a constant repeat of each degree until it was parallel to the sides it was different.
#$&*
Describe how you would orient the bracket to obtain the most regular 'beat' of the pendulum.
Your response (start in the next line):
After observing and counting the 'beats' that it would do against the bracket the best regular 'beat' of the pendulum is when the bracket is parallel to the side of the book.
#$&*
Orient the bracket in this position and start the TIMER program. Adjust the pendulum to the maximum length at which it will still bounce regularly.
Practice the following procedure for a few minutes:
Pull the pendulum back, ready to release it, and place your finger on the button of your mouse. Have the mouse cursor over the Click to Time Event button. Concentrate on releasing the pendulum at the same instant you click the mouse, and release both. Do this until you are sure you are consistently releasing the pendulum and clicking the mouse at the same time.
Now you will repeat the same procedure, but you will time both the instant of release and the instant at which the pendulum 'hits' the bracket the second time. The order of events will be:
click and release the pendulum simultaneously
the pendulum will strike the bracket but you won't click
the pendulum will strike the bracket a second time and you will click at the same instant
We don't attempt to time the first 'hit', which occurs too soon after release for most people to time it accurately.
Practice until you can release the pendulum with one mouse click, then click again at the same instant as the second strike of the pendulum.
When you think you can conduct an accurate timing, initialize the timer and do it for real. Do a series of 8 trials, and record the 8 time intervals below, one interval to each line. You may round the time intervals to the nearest .001 second.
Starting in the 9th line, briefly describe what your numbers mean and how they were obtained.
Your response (start in the next line):
1 15060.46 15060.46; 2 15060.97 .5039063
1 15089.96 15089.96; 2 15090.31 .3515625
1 15105.09 15105.09; 2 15105.42 .3320313
1 15157.5 15157.5; 2 15158 .5039063
1 15181.81 15181.81; 2 15182.17 .359375
1 15207.86 15207.86; 2 15208.34 .4882813
1 15233.54 15233.54; 2 15234.01 .4726563
1 15272.39 15272.39; 2 15272.93 .5351563
There are eight trials that I have conducted. Each one is the same way; in which I pull the pendulum, let go of it and at the same time click the timer, then click the timer again when the 'pearl' hits the bracket a second time. The intervals shows how long it takes the pearl to hit the bracket from the beginning (from when I let go) to the second time it hits the bracket.
#$&*
Finally, you will repeat once more, but you will time every second 'hit' until the pendulum stops swinging. That is, you will release, time the second 'hit', then time the fourth, the sixth, etc..
Practice until you think you are timing the events accurately, then do four trials.
Report your time intervals for each trial on a separate line, with commas between the intervals. For example look at the format shown below:
.925, .887, .938, .911
.925, .879, .941
etc.
In the example just given, the second trial only observed 3 intervals, while the first observed 4. This is possible. Just report what happens in the space below. Then on a new line give a brief description of what your results mean and how they were obtained.
Your response (start in the next line):
.5351563, .6796875, .6875, .671875, .640625, .703125 , .7265625, .6171875, .6328125, .7109375
.5742188, .671875, .65625, .6835938, .71875, .7421875
.6171875 .6484375 .6171875 .5898438 .6796875 .7382813 .65625
.6171875 .6484375 .6171875 .5898438 .6796875 .7382813 .65625
The given numbers are the intervals for each trail. The intervals consisted of when the 'pearl' hit the bracket on the second time (2nd, 4th, 6th, etc).
#$&*
Now measure the length of the pendulum. (For the two-pearl system the length is measured from the bottom of the 'fixed' pearl (the one glued to the top of the bracket) to the middle of the 'swinging' pearl. For the system which uses a bolt and magnet at the top instead of the pearl, you would measure from the bottom of the bolt to the center of the pearl). Using a ruler marked in centimeters, you should be able to find this length to within the nearest millimeter.
What is the length of the pendulum?
Your response (start in the next line):
The length of my pendulum is approximately 17.4 cm (this is from the top of the bracket to where the string is attached to the 'pearl').
#$&*
If you have timed these events accurately, you will see clearly that the time from release to the second 'hit' appears to be different than the time between the second 'hit' and the fourth 'hit'.
On the average,
how much time elapses between release and the second 'hit' of the pendulum,
how much time elapses between the second and fourth 'hit' and
how much time elapses between the fourth and sixth 'hit'?
Report your results as three numbers separated by commas, e.g.,
.63, .97, .94
Your response (start in the next line):
.5351563, .6796875, .6875
#$&*
A full cycle of a free pendulum is from extreme point to equilibrium to opposite extreme point then back to equilibrium and finally back to the original extreme point
(or almost to the original extreme point, since the pendulum is losing energy as it swings)..
The pearl pendulum is released from an 'extreme point' and strikes the bracket at its equilibrium point, so it doesn't get to the opposite extreme point.
Does an interval consists of motion from extreme point to equilibrium, or from equilibrium to extreme point, how many intervals occur between release and the first 'hit'?
Your response (start in the next line):
The interval consists of motion from extreme point to equilbrium. There will be one interval.
#$&*
How many intervals, as the word was described above, occur between the first 'hit' and the second 'hit'? Explain how your description differs from that of the motion between
release and the first 'hit'. If we are defining an interval from when it is released, hits the equilibrium, then to exreme position then it would be one interval for the first 'hit.'
Your response (start in the next line):
There will be four intervals that occur between the first and second 'hit.' That is if we are defining an interval to be from the extreme position to the first hit.
If we are defining an interval from when it is released, hits the equilibrium, then to exreme position then it would be one interval for the first 'hit.' Then there will only be one interval because it only did it once from extreme position to extreme position again and when it does a second 'hit' it only has done half an interval because it hasn't gone back to its extreme position again.
#$&*
@&
An interval is from extreme position to equilibrium position, not from extreme to extreme.
To get to the second 'hit' the pendulum has to swing back from release at the extreme position to the equilibrium position. Then to hit a second time it has to swing from extreme to equilibrium once more. That's two intervals.
What else does it have to do?
*@
How many intervals occur between release and the second 'hit', and how does this differ from the motion between the second 'hit' and the fourth 'hit'?
Your response (start in the next line):
There has been one interval that has completed.
For the motion in it being a second 'hit' and fourth 'hit there would be two intervals that have completed because it went from extreme positon -> equilibrium -> extreme position twice.
#$&*
How many intervals occur between the second 'hit' and the fourth 'hit', and how does this differ from a similar description of the motion between the fourth 'hit' and the sixth 'hit'?
Your response (start in the next line):
Two 1/2 intervals. Because in this one we are defining an interval from extreme position -> equilbrium ('hit') -> extreme position
If we are defining an interval from the point of equilibrium (which I think this is the case because the second hit would be an interval) to an extreme position then equilibrium then for a motion between fourth 'hit' and sixth 'hit there will be two intervals that have completed.
#$&*
Why would we expect that the time interval between release to 2d 'hit' should be shorter than the subsequent timed intervals (2d to 4th, 4th to 6th, etc.)?
Your response (start in the next line):
I think that the time interval between released to 2d 'hit would be shorter because it is the beginning of the pendulum then it gets into a rhythm.
#$&*
Would we expect additional subsequent time intervals to increase, decrease or stay the same?
Your response (start in the next line)
I would expect the additional time intervals to stay the same since it would be constant.
#$&*
What evidence does this experiment provide for or against the hypothesis that the length of a pendulum's swing depends only on its length, and is independent of how far it actually swings?
Your response (start in the next line):
I think it goes for the hypothesis that the length of the pendulum swing depends on its length because of the given intervals that are done in between the given 'hits'
#$&*
Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades:
Approximately how long did it take you to complete this experiment?
Your response (start in the next line):
1 hr 40 minutes
#$&*