Finding g from a Compound Pendulum Graph

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Homework Help Overview

The discussion revolves around a compound pendulum experiment aimed at determining the acceleration due to gravity (g) from a graph related to the pendulum's oscillation periods. The original poster describes the setup and the method for calculating g, but expresses confusion regarding the interpretation of the graph and the selection of periods for analysis.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to clarify the method for calculating g from the graph, questioning how to select the period T and the process for averaging T values. Some participants suggest that visual aids, such as sketches or pictures, would enhance understanding of the setup and graph interpretation.

Discussion Status

The discussion is ongoing, with participants exploring the original poster's questions about the methodology and the need for visual clarification. There is no explicit consensus yet, but the suggestion for visual aids indicates a productive direction for the conversation.

Contextual Notes

The original poster notes a lack of clarity regarding the selection of the period T and the method for averaging T values, which may impact their understanding of the experiment's requirements.

Motorbiker
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Thread moved from the technical forums, so no HH Template is shown.
I am doing the compound pendulum experiment but I am stuck on how to find the value of g from the graph

Here's a description of the compound pendulum:

The compound pendulum AB is suspended by passing a knife edge through the first hole. The pendulum is pulled aside through a small angle and released, whereupon it oscillates in a vertical plane with a small amplitude. The time for 10 oscillations is measured. From this the period T of oscillation of the pendulum is determined.

The method to find the acceleration due to gravity, is not really making much sense.

Please see it below:

A graph is drawn with the distance d of the various holes a straight line is drawn parallel to the X- axis from a given period T on the Y- axis, cutting the graph at four points A, B, C, D. The distances AC and BD, determined from the graph, are equal to the corresponding length l. The average length l = (AC+BD)/2. In a similar way , l/T2 is calculated for different periods by drawing lines parallel to the X-axis from the corresponding values of T along the Y- axis. l/T2 should be constant over all periods T, so the average over all suspension points is taken. the acceleration due to gravity is calculated from the equation g= 4π2(l/T2).

I don't know what the given period is, do you just use any random period? For I/T2, do you just like draw vertical lines parallel to all the values of T and then average the T values?
 
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This would so be so much easier to understand with a sketch of the setup and a picture of the graph.
 
I won't be able to upload a sketch of the setup since my printer isn't working at the moment.

Is it okay if I show you an accurate picture of the experiment and a picture of the graph? :smile:
 
Motorbiker said:
Is it okay if I show you an accurate picture of the experiment and a picture of the graph?
That's a good start! :smile:
 

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