Find the Tensions in the Cables

  • Thread starter Northbysouth
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In summary, to determine the tensions in cables AB, AC, and AD, the unit vectors of each cable were found and multiplied by the given force. After correcting a mistake in the location of point B, the tensions were calculated to be TAB = 41.9316, TAC = 41.9316, and TAD = 50.7184.
  • #1
Northbysouth
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Homework Statement



Determine the tensions in cables AB, AC, and AD.


Homework Equations





The Attempt at a Solution


I mad point A (0,0,0)
B = (2.6, -4.2, 4.4)
C = (-2.6, -1.6, 4.4)
D = (0, 2.5, 4.4)
Firstly I found the unit vectos of AB, AC and AD, which are as follows

[itex]\hat{}n[/itex]AB = <2.6, - 4.2, 4.4>/ 6.615134

[itex]\hat{}n[/itex]AB = <0.393041i - 0.634908j + 0.665141k

[itex]\hat{}n[/itex]AC = <-2.6, -1.6, 4.4>/5.35537

[itex]\hat{}n[/itex]AC = <-0.48549i -0.29876j +0.821605k>

[itex]\hat{}n[/itex]AD = <0i +2.5j + 4.4k>/5.06063
[itex]\hat{}n[/itex]AD = oi + 0.494009j + 0.86945k

Then I took each unit vector and multiplied it by the force, 113 lb

TAB = TAB[itex]\hat{}n[/itex]AB[/SUB = TAB(0.39394i - 0.634908j + 0.665141k)

TAC = TAC[itex]\hat{}n[/itex]AC = TAC(-0.48549i -0.29876j + 0.821605k)

TAD = TAD[itex]\hat{}n[/itex]AD =TAD(0i + 0.494009j +0.86956k)

i: 0.39304*TAB - 0.48549TAC + 0TAD

j: -0.634908TAB - 0.29876TAC + 0.494009TAD

k: 0.665141TAB + 0.821605TAC + 0.86945TAD

I then put this into a matrix and then used my calculator to solve for TAB, TAC and TAD

I got:

TAB = 39.3261
TAC = 31.9374
TAD = 69.7967

But it says my answer is wrong and I don't know where I'm going wrong. Help would be appreciated
 
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  • #2
Just found my mistake. I defined the location of B incorrectly. B = (2.6, -1.6, 4.4). Using these values I get

TAB = 41.9316
TAC = 41.9316
TAD = 50.7184
 

Related to Find the Tensions in the Cables

What is the purpose of finding the tensions in the cables?

The purpose of finding the tensions in the cables is to determine the forces acting on the cables in order to design a safe and stable structure. This information is crucial in the construction of bridges, buildings, and other structures.

How do you calculate the tensions in the cables?

The tensions in the cables can be calculated using the equations of equilibrium, which states that the sum of all forces acting on a stationary object must be equal to zero. By setting up and solving equations for each cable, the tensions can be determined.

What factors can affect the tensions in the cables?

There are several factors that can affect the tensions in the cables, including the weight and distribution of the load, the angle and direction of the cables, and the strength and elasticity of the materials used for the cables.

How do you ensure the accuracy of the tension calculations?

To ensure the accuracy of the tension calculations, it is important to use precise measurements and accurate data for all variables. It is also crucial to consider any external factors that may affect the tensions, such as wind or temperature, and to account for them in the calculations.

What are some common methods for measuring the tensions in cables?

Some common methods for measuring the tensions in cables include using strain gauges, load cells, and dynamometers. These devices can accurately measure the forces acting on the cables and provide valuable data for tension calculations.

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