Assignment help - Determining bearing friction?

[bikertomm]

Hi all, I'm new to the forum and have a query with one of my most recent assignments.

This one is called 'The flywheel' to do with moments of inertia. I have completed the first lot of calculations using the formula no problem.

My average experimental value came out at 0.49 kg m(2)

And the theory calculation came out at 0.50 kg m(2)

Question 2 & 3 are the ones I'm struggling with:

Question number 2 says to discuss the effect of bearing friction - I am really struggling to find anything on this.

Question 3 asks how the effect of friction can be determined? I'm struggling with this too. Any help would be massively appreciated..

Here are some pictures of the assignment, cheers.

 

[haruspex]

Just as linear friction is a force opposing relative motion of two bodies with flat surfaces in contact, bearing friction is a torque opposing relative rotational motion about the bearing's axis of two bodies in contact. Again, there will be a static value, typically larger than the kinetic value. Does that help?

 

[andrevdh]

Q2. You most likely did not take the frictional torque into consideration in your experiment.
It opposes the rotational motion thereby decreasing the net torque acting on the
flywheel. Consider how this would influency your measurement of falling time
and thus the experimental value of the moment of inertia of the flywheel.

Q3 Asks how you can put a value to this frictional effect.
Can you maybe calculate by how much it changed the
falling time?