Physics, Moment of Inertia Please help Today!?

Question

Hello,

I have some questions:

1. Do you think the calculated moment of inertia is larger or smaller than the true moment of inertia? Explain.

for static moment of inertia I have:.0202kgm^2
for dynamic " ":.0195 kgm^2

In this case, it's smaller but I don't know why.

2. Is the percent difference in accord with your answer to #2? Give plausible explanations/causes to account for the difference. for the percent difference I got 3.6% which is small so it does agree with #2. I am not sure why there is a difference though.

3. The wheel could replace the pulley on newton's law's 2nd law. Try to rethink an answer to the question: "If the pully has a fairly large mass, how will the result of this experiment be affected? "

Answer 1

This is half a question! Would you be able to understand this question without more info? Are answerers supposed to be clairvoyant? But... read on.
How was the calculated MI calculated? Experimentally?
You show a 3.6% error. This could be considered reasonable experimental/measurement error. Could you have ignored (perhaps you were told to ignore) some contributors to error, such as: mass of a connecting string; error in pulley diameter (exactly what length of string per revolution can be difficult to determine because of string thickness); error in effective radius of mass of pulley (if it's the pulley MI you're dealing with) or wheel. Add more information to this Q via the "Additional Details" option and you may get a better answer.

Answer 2

Hi Diamond! Does it mean you are doing a lab?
If so then the value of .0195 is more likely to be closer to real one from above, because the kinetic friction is always less than static friction. If this is true then your “fairly massive” pulley would have the same percentage of reliability of your result, while the absolute difference in units of kg*m^2 would be larger than that for a lighter pulley.