Re: Moment of Inertia Lab: huge error in slope and intercept values for graph from Experiment 2

by MattChequers Sat Mar 02, 2013 6:09 pm

You should have an uncertainty value for every measurement in the labs. In the end, I think the important part of the labs is: yes, to develop various techniques but also to carry out a good analysis, and interpret the final results. Glad that you got it all sorted out!

by Danielle.Mayo Fri Mar 01, 2013 5:14 pm

It turns out that we plotted x and y backwards when making our graph, which cause the huge error. However, just out of curiosity, should we have weighed the masses used in part 2 ourselves? Obviously if we had weighed them then there would be uncertainty in that measurement, however we didn't so we took the mass values to be perfect. I was under the impression that we weren't supposed to weigh them, however I could be mistaken.

Thanks!

by MattChequers Wed Feb 27, 2013 1:03 pm

You should always have an uncertainty with every measurement you make. The only parameters that have zero uncertainty in this lab are the mass of the wheel and the small mass used in part 3. There is no real way to fix this now since what's done is done. There are no "wrong" answers in the lab. The exercise of the labs is to be able to explain final results, whether they agree or not. As a side note, it is unethical to assign an uncertainty value, in hind sight, to fix the results.

by Danielle.Mayo Wed Feb 27, 2013 11:16 am

We used the linear regression spreadsheet from the moodle page to generate our plots for this lab, which worked well. However when we assumed that there was no error in the mass values for experiment two, the uncertainty values for the slope and intercept became large in comparison to the actual values (+/-170840 and +/-1332 respectively). This will make the uncertainty in the moment of inertia and torque calculations huge. Is there a way to fix this?

Thanks!

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