Impossible angular acceleration problem

[royguitarboy]

Impossible "angular acceleration" problem

Homework Statement

The figure below shows a hollow cylindrical tube of mass M = 1.2 kg, L = 1.9 m, and moment of inertia ML2/10. Inside the cylinder are two disks of mass m = 0.6 kg, separated by a distance l = 0.8 m, and tied to a central post by a thin string. The system can rotate about a vertical axis through the center of the cylinder. The system rotates at (omega) such that the tension in the string holding the disks is 108 N just before it breaks. When the disks reach the end of the cylinder, they stick. Assume that the inside walls of the cylinder are frictionless. Determine the initial and final angular velocities of the system.

Homework Equations

Lf=Li
L=(moment of inertia)(omega)

The Attempt at a Solution

I'm not sure how to set this up. Any hint or help on how to set it up would be greatly appreciated.

 

[anathema]

I can understand your frustration with this problem. It does seem quite challenging and even impossible at first glance. However, as with any problem in science, there is always a solution.

First, let's break down the problem into smaller, more manageable parts. We have a hollow cylindrical tube with two disks inside, tied to a central post by a string. The system is rotating about a vertical axis. This means that we are dealing with rotational motion and we can use the equations for rotational dynamics.

We are given the mass and length of the cylinder, as well as the moment of inertia. We also know the mass and separation distance of the disks. Using these values, we can calculate the moment of inertia of the entire system.

Next, we are given the tension in the string just before it breaks. We can use this information to calculate the initial angular velocity of the system using the equation L=(moment of inertia)(omega).

Once the disks reach the end of the cylinder and stick, the system will have a new moment of inertia. However, since the walls of the cylinder are frictionless, there will be no external torques acting on the system and the angular momentum will be conserved. This means that the final angular velocity can be calculated using the equation L=(moment of inertia)(omega).

So, to summarize, we can use the equations for rotational dynamics to calculate the moment of inertia of the system, the initial angular velocity, and the final angular velocity. I hope this helps you to set up the problem and find a solution. Remember, as a scientist, it's important to approach problems with curiosity and perseverance. Don't give up, and you will find a solution. Good luck!

 

[ogb p]

I would first clarify the problem and make sure all the given information is correct and relevant. I would also double check the equations and make sure they are applicable to the problem. In this case, the given information seems to be inconsistent and the equations may not be applicable.

The problem states that the system can rotate about a vertical axis through the center of the cylinder, but then it mentions the disks reaching the end of the cylinder and sticking. This would imply that the cylinder is not rotating about its center, but rather about its end. This would also change the moment of inertia of the system, making the given value of ML2/10 invalid.

Additionally, the tension in the string holding the disks is given as 108 N, but this value is dependent on the angular velocity of the system. It cannot be used to determine the initial and final angular velocities.

Without a clear and consistent problem statement, it would be impossible to solve this problem. As scientists, it is important to critically evaluate and clarify information before attempting to solve a problem.