Torque for rotating a shaft of unbalanced weight

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Homework Help Overview

The discussion revolves around calculating the torque required to rotate a shaft with two unbalanced masses positioned at 120-degree angles. The problem involves understanding the forces acting on the shaft due to the masses and their respective lengths.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the need for the lengths of the bars and question how to calculate torque based on the given masses and angles. There is a focus on whether to consider the total mass or calculate a resultant mass, as well as the implications of the lengths of the bars on the torque calculation.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. Some guidance has been offered regarding the relationship between torque, force, and length, but there is no consensus on the correct approach to take regarding the masses and their configuration.

Contextual Notes

Participants are working under the assumption that both masses are of equal length, despite visual discrepancies in the provided drawing. There is also uncertainty about the correct formula to use for torque calculations.

sekar_507
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1. Hi all. Can anyone please help me find the torque required for rotating a shaft which has two masses 1000 Kg each at 120 Degree angles. Please refer to the attachment for clarity.



Homework Equations





The Attempt at a Solution

 

Attachments

  • Torque calc.JPG
    Torque calc.JPG
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I think you need the lengths of the two bars.
 
The bars are 500mm long each. How do I calculate the torque?
 
Torque = force times length.
So, what do you think you should use for length and force?

You sure the bars are of equal length? Looks like bar 1 is longer than bar 2.
 
Last edited:
should i use formula torque = I * Angular velocity for calculating the torque for rotating the shaft? Please clarify
 
No, since that's the formula for angular momentum, not torque.
 
ok then. since both the masses are at 120 deg angle. what is the total mass i should i consider. should i add 1000+1000 = 2000 Kg or should i calculate the resultant mass? can u help me in finding the resultant mass?
 
You never answered my question: are you sure the masses are of equal length?
 
Yes. Both the masses are of equal length.
 
  • #10
OK, (though I'm still wondering why the drawing shows them as clearly of different lengths).

How about writing an expression for the torque about the axis of rotation as a function of angular position? You can call zero angle at any position you like.

Take one bar at a time. What's the torque gravity applies to one of the bars as a function of its angular position?
 
Last edited:

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