Science Buddies: "Ask an Expert"

Hi, i'm doing a big physics project and i'm supposed to think of a non-trivial research question, investigate it, make a report, etc. So, my question is 'How does the length of a pendulum affect its time period', so my independent variable is the length of the string attached to a ball, my independent variable is the time taken for 20 oscillations of the ball and my constant is the average force I swing the ball with(this is going to be a rough estimate). So, my questions are:
1)any guidance/advice that will make this experiment better(or more accurate)
2)is the topic too trivial(would i be able to write about 5500 words on it or close)
3)I've been carrying out test runs of the experiment(and as i shorten the string, the ball moves faster which is good because that was my hypothesis) but i've been looking for an explanation and I haven't been able to find one...any ideas?
,thank you.

Hello happyme,

Based on your description of your experiments I do have a couple of suggestions.

First, I would not try to swing the ball with a constant force. Instead I suggest that you release the ball from a constant angle relative to vertical. That way you can measure the angle and reproduce it for each of your experimental trials.

Also, I would plan on completing 4 or 5 trials for each string length. That way you find out how variable your results are and you can average your results.

I am not a teacher and I am not in a position to evaluate whether your topic is “too trivial”.

A good explanation of pendulum motion is at this link:
http://www.physicsclassroom.com/class/w ... lum-Motion


Good luck with your project and please post again if you have more questions.

A. Norman

Hi Happy Me,
I agree with the previous expert's suggestion that you run the experiment with several different lengths of string AND that you run the experiment 4-5 times for each length.

As the previous expert points out, you will then be able to evaluate the variability within trials for each length of string. What I particularly like is that you will also be able to see if the length of string affects the variability within trials for each length.

If you wanted to add more complexity, you could add angle as a variable. This should definitely provide sufficient complexity so that you have a very interesting and non-trivial project!

Let us know how this works out and if you have more questions!