How Should Angles Be Used in Calculating Tension Forces?

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Homework Help Overview

The discussion revolves around calculating tension forces in a system involving multiple cables at different angles. The original poster describes their approach to resolving the components of tension forces T1, T2, and T3, while expressing uncertainty about the correct angles to use in their calculations.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to calculate the x and y components of tension forces using trigonometric functions but is unsure about the angles to apply. They present their calculations and seek clarification on the correct approach.

Discussion Status

Some participants provide feedback on the original poster's calculations, pointing out potential sign errors and clarifying angle conventions. There is an indication that the discussion is progressing towards a clearer understanding of the angle usage, but no consensus has been reached on the correct solution yet.

Contextual Notes

The original poster mentions a specific figure that is not included in the text, which may contain crucial information for resolving the problem. Additionally, there is an emphasis on the need for correct angle interpretation in the context of the problem.

cbchapm2
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Homework Statement


See attached figure below for problem:
CH4C WA.jpg

I'm designating the "horizontal cable" T1, the "incline cable" T2, and the "vertical cable" T3.

Homework Equations


I used the following to find x and y components of each force:
x comp=Tncos(theta)
y comp=Tnsin(theta)

The Attempt at a Solution



I made a chart for T1, T2, and T3 for the respective x and y components.
T1:
x=T1cos(180)
y=0 (because it's only the x direction)
I didn't know which angle to use for theta, I used 180 because of where I put the x and y-axis in my free body diagram.

T2:
x=T2cos(38)
y=T2sin(38)
Again, I didn't know if I should use the 38* or add 180 to it...

T3:
x=0 (because it's only in the y direction?)
y=532 N (given)

I started to sum my x components and then solve for T2, but the answer that I got was wrong. I did this:
Sun of x components: 0=T1cos(180)+T2cos(38)
T2=T1(cos(180)/cos(38))
T2=1.27 N
I tried both 38* and 218* for the theta of T2 and both answers were wrong.

Sum of y components: 0=T1sin(180)+T2sin(38)+532N
Once I got the correct value for T2, I would plug it into this equation to find T1. And T3 will equal the weight (532 N) because of equilibrium, right?

Can anyone help me get on the right track?

Thanks!
 
Last edited:
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cbchapm2 said:
Sun of x components: 0=T1cos(180)+T2cos(38)
T2=T1(cos(180)/cos(38))
You've switched the sign there.
T2=1.27 N
Where did that come from?
Sum of y components: 0=T1sin(180)+T2sin(38)+532N
To be consistent with the signs, that should be -532N (sin(270)=-1).
 
You have some confusion with angles. The convention is that the positive x- axis has angle 0 degrees, and the angle increases as one goes counterclockwise. Therefore, positive y is 90 degrees, negative x is 180 degrees and negative y is 270 degrees.
 
I got the right answer! When I solved the first equation for T2, I dropped the T1 and it threw off everything else too.
 

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