Static Equilibrium and tension of a cord

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Homework Help Overview

The problem involves a non-uniform bar suspended in static equilibrium by two massless cords, with a focus on calculating the tension in one of the cords. The scenario includes specific measurements such as the weight of the bar, the angle of one cord, and the distance of the center of gravity from one end of the bar.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the equations of force and torque, questioning the correctness of the torque equation and the appropriate length to use in calculations. There is uncertainty about which cord is referred to as cord 1 and the dimensions involved in the torque calculation.

Discussion Status

Some participants have confirmed the equations for forces in the x and y directions, while others are exploring the implications of using different lengths in the torque equation. There is ongoing clarification regarding the dimensionality of the torque equation and the correct interpretation of the forces involved.

Contextual Notes

Participants are grappling with the definitions of terms and the setup of the problem, particularly regarding the dimensions used in the torque calculations and the identification of the cords. There is a lack of consensus on the correct approach to the torque equation.

chaotixmonjuish
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A non-uniform bar of weight W = 12.5 N is suspended at rest in a horizontal position by two massless cords. The angle φ between cord 2 and the vertical is equal to 27.5°. The bar has a length L = 6.0 m and the distance of its center of gravity from the left-hand end of the bar is 4.4 m. What is the tension in cord 2?
img:http://i242.photobucket.com/albums/ff106/jtdla/prob01a-2.gif

My lab partner and I set up this equation:
Fx: T2*cos (27.5)-T1*cos(theta)=0
Fy: T2*sin(27.5)+T1*sin(theta)-mg=0

Torque: -mgL-T2*cos(27.5)=0

I'm not sure if that L is 4.4 or 6, nor do I know if I am starting this properly.
 
Last edited by a moderator:
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Eqn for Fx and Fy are correct, but torque is incorrect; firstly, dimensionally its wrong and secondly, which is cord 1? left side one or right side one?
 
Cord 1 is on the left
 
k. then L should be 4.4
 
so is the torque equation correct if i use 4.4
 
dimensionality?
 
I'm afraid I don't understand
 
chaotixmonjuish said:
Torque: -mgL-T2*cos(27.5)=0
T2*cos(..) has dimensions of force and mgL has dimensions of work.
 
so would torque be the length of the bar*-mg
 
  • #10
torque is : -mgL + T2cos(27.5)*6 (6 is the perpendicular distance of force vector from the point at which you are taking torque)
 
Last edited:

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