I'm running an experiment in a video-game simulator (ish) called 'G-MOD'. I setup a typical pendulum setup, and measured the change in the period as a function of the pendulum's mass. I obviously expected the pendulum's period to remain a constant regardless of the change in mass. However, to my surprise, I noticed that as the mass increased there was a general positive increase of the period.

At first, I blamed air resistance; however from my knowledge air resistance shouldn't be impacted by the mass of an object, but only by its shape (aerodynamics), and since this is a video game I was able to make the shape of the pendulum bob identical while changing its mass.

I only possess a high-school level of understanding for physics, and I can't think of a reason as to why the mass would affect the period of a pendulum. Could anyone think of any answers to the pondering?

@Philip Here is the data pics To clarify some things first, the masses were all in kg, the 'unit' listed is in game units; but through the developer's website I found some sort of conversion factor so I changed it to 'metres'.

This is the 'big range' of my independent variable. You can see I kinda gave up measuring for the unstableness reason I stated: enter image description here

The second dataset is for the 'smaller range': jj

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    $\begingroup$ may be the physics of the video game is not very accurate $\endgroup$
    – user65081
    Oct 18, 2020 at 16:36
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    $\begingroup$ or maybe it is so good that it it detecting the change in the moment of inertia of the mass. A pendulum NOT made of a point particle has a period dependent on the mass distribution. What shape is your pendulum and how are you changing its mass? $\endgroup$
    – JalfredP
    Oct 18, 2020 at 16:59
  • $\begingroup$ Is the density of the pendulum bob changing, or is its size growing? In the second case, it will add to the angular inertia, thus increasing the period. $\endgroup$
    – dominecf
    Oct 18, 2020 at 17:34
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    $\begingroup$ Hi. This is an interesting question, but as such I don't think it can be answered well. Do you think you would be able to add some data to your question? I'd be very interested to see what it looks like. How are you measuring the period? Over how many oscillations are you averaging? What is the amount of change that you notice? What does the system look like (is it composite or "simple", as @JalfredP asks)? A lot of the time (even in real experiments) "increases" are inferred even when there are none, since the increase lies within range of uncertainties of the value itself. $\endgroup$
    – Philip
    Oct 18, 2020 at 17:53
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    $\begingroup$ @Maruwan Possibly, also if you are including the mass of the rod, then a heavier bob will lower the center of mass of the rod and bob. $\endgroup$ Oct 19, 2020 at 22:50