Static Equilibrium of mass and wire

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Homework Help Overview

The discussion revolves around a static equilibrium problem involving a mass supported by a wire attached to a steel bar, which is pivoted at a wall. The problem includes calculations for tension in the cable and forces exerted by the wall on the bar, with specific reference to the setup and dimensions provided.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the calculations for tension and forces, with some attempting to derive the tension in a modified setup. There are questions about the correctness of initial calculations and the need for clarification on the problem's diagram.

Discussion Status

Some participants have successfully completed part (a) of the problem and are seeking assistance for part (b). There are ongoing attempts to correct and refine calculations, with various interpretations of the problem setup being explored.

Contextual Notes

Participants note the importance of the diagram for understanding the problem, and there are indications of confusion regarding the application of trigonometric functions in the calculations. The need for accurate tension values to proceed with further calculations is emphasized.

chara76
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Homework Statement



A 345 kg mass is supported on a wire attached to a 15 m long steel bar that is pivoted at a vertical wall and supported by a cable. The mass of the bar is 95 kg. (Take right and up to be positive.)

http://img522.imageshack.us/img522/8374/1265alt.gif"

(a) With the cable attached to the bar 5.0 m from the lower end as shown, find the tension in the cable.
10003.6976 N (Done)

Find the force exerted by the wall on the steel bar.
5001.8488 N i + -4347.056 N j (Done)

(b) A somewhat longer cable replaces the old and is attached to the steel bar 5.0 m from its upper end, connecting to the same place on the wall as before and maintaining the same angle between the bar and the wall. Find the tension in the cable.
? N

Find the force exerted by the wall on the steel bar.
? N i + ? N j

Homework Equations



Sum of Torques = 0
Sum of Fy = 0
Sum of Fx = 0

The Attempt at a Solution



(b)
[(95kg)(9.81)(7.5m)(cos60) + (345kg)(9.81)(15m)(cos60)] / 10m
= 2887 N This is wrong

I haven't attepmted the second part of B because I need the tension to do so.
 
Last edited by a moderator:
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unable to portrait the picture of problm..
can you please put up the figure..
 
Added link to picture. Sorry about that
 
it shud be:
[(95kg)(9.81)(7.5m)(sin60) + (345kg)(9.81)(15m)(sin60)] / (10cos30)
 
I have this same problem, but I already got part a. Can someone please help me find part b?
 
I found the force, and the force in the i direction, but not in the j...
 

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