Is my tutor wasting my time?

[broouk]

Homework Statement

This is the first part of a more complex problem but I shall give all the relevant data. A cast iron flywheel is rotating at 80rev/sec and is brought to rest in 20sec by a hydraulic braking system acting on the outer dia. of the flywheel. There is 4Nm of frictional torque in the flywheel system and co-efficient of friction of the brake interface is 0.4. I need to find the force that the brake is exerting on the flywheel. For info the brake is then connected to 2 hydraulic cylinders, of different areas, in series and then to a second order lever. However, if I can find the force at the brake I can crack the rest. I have not been given a moment of inertia or a radius for the flywheel and the more time I spend trying to solve this, the more I think that my tutor has made a mistake in not giving one of these.

Homework Equations

initial ang. velocity is 502.65 rads/sec before the braking

T=Fr and F=(co-eff. of friction)*N

Therefore T=co-eff.*N*r

The Attempt at a Solution

I started trying to use the above equations but the only T value I have is for frictional torque.
The only moment of inertia value I can get is also using this fric. torque which is incorrect, I think.
By converting rev/sec to rads/sec=502.65 I can also find the radians rotated by the flywheel. radians=1/2 (initial velocity+final velocity)*t
=5026.5 radians
Still can't seem to get anywhere with this. Do I need a moment of inertia or radius to get any further?

 

[kamerling]

There's indeed no way you can do it without the moment of inertia. I

 

[Moetasim]

I understand your frustration with not being given all the necessary information to solve a problem. It is always important to have all the relevant data in order to accurately solve a problem and come to a correct conclusion. However, I would not jump to the conclusion that your tutor is wasting your time. It is possible that they may have overlooked including the moment of inertia or radius, but it is also possible that they want you to think critically and find a way to solve the problem without those values. This type of problem-solving can be valuable in the real world, where not all information is always readily available.

I would suggest discussing your concerns with your tutor and seeing if they can provide any additional guidance or clarification. If they do not have the missing information, they may be able to point you in the right direction for finding it or suggest alternative methods for solving the problem. As a scientist, it is important to approach problems with an open mind and be willing to adapt your methods if necessary. Best of luck in finding a solution to this problem.