Because I was quite late this meeting, it was quite disorienting to see my other labmates already starting a new experiment as I entered the room. The setup that I chanced upon seeing involved a stand, a pendulum, a set of weights and a string. Immediately, simple harmonic motion entered my mind - this week's experiment was all about pendulums. It was something very familiar to me since I already did a variation of this experiment back in High School.
Mac and I formed a new group, since both of us were late. Peter, our other group mate, was absent this meeting. We went upstairs to the physics instruments room to get the setup and what greeted us inside the room was a very upset and grumpy man who handled the materials. I don't want to rant about the old man but it seemed as if he was grumpy for no apparent reason. It irritated me a bit as to how he acted- it was unethical, yes, and also quite unnecessary.
After getting the materials, we went back to the room and started the experiment. Basically, what we were supposed to do was to vary the length of string, angle of displacement, and weight of bob one at a time to see their effect on the period of oscillation.
Since there were only two persons in our group, both of us had to do something. Mac measured the period of oscillation, while I fixed the angle of displacement and released the bob. Like all the other experiments that we have performed, this one was very routinary and involved trial upon trial.
The motion of a pendulum could be described by a mathematical equation:
T=2*pi*sqrt(L/g)
where T=period, L=length of string, and g=gravitational acceleration.
As we can see from the formulation, the only major contributing factor to the period is the length of string. Their relationship is direct- increasing L increases T. After some research, I also discovered that T is also affected, to some extent, by the angle of displacement, i.e. the equation only works for small angles of displacement. For large angles, more complicated mathematical formulations that involve Taylor expansions and infinite series are required.
The data that we gathered, as far as I can remember, are not that concise with the theoretical expectations. We measured slight increases in period of oscillation as we increased the mass. This could be attributed to error in release of bob or in measurement of time.
Since we were late for the meeting, we were unable to test the scenario wherein the length was very, very high, thereby we had to merge with Robby's group to share with their data. It was very fun because the setup was too big for R108; we had to go to the second floor and hang the pendulum from that height. Admittedly, the setup was quite dangerous since the bob could fling from the string and hit bystanders, but still, it was very fun. For this setup, I was assigned to measure the period of oscillation.
I prefer this experiment to the two previous projectile motion experiments because
1. I was reunited with my old group, even if the other member was absent
2. I was more useful in this experiment
3. the setup was generally more fun (particularly the large L setup)
This new experiment implied that we had to, again, submit a technical report next meeting, something that I'm really not that enthusiastic about.
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