Calculating Tension in a Horizontal Clothesline with Vectors

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Homework Help Overview

The problem involves calculating the tension in a horizontal clothesline that sags due to a mass attached to it. The scenario includes specific measurements, such as the distance between the poles and the sag distance when a mass is applied.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the tension using force components and trigonometric functions, while others question the validity of the answer based on feedback from an automated checker.

Discussion Status

The discussion reflects a mix of attempts to validate the calculations and explore potential issues with the automated feedback. Some participants suggest that minor details, such as the value of gravitational acceleration, could affect the outcome.

Contextual Notes

The original poster notes that the problem is presented in an online format that provides feedback, indicating that precision in numerical answers is crucial.

Mark Nussbaum
Moved from a technical forum, so homework template missing
For some reason I'm really struggling to get a correct answer on this problem

"A horizontal clothesline is tied between 2 poles, 20 meters apart.
When a mass of 3 kilograms is tied to the middle of the clothesline, it sags a distance of 4 meters.

What is the magnitude of the tension on the ends of the clothesline?"

Work:
Fg = 3kg*9.81m/s^2 = 29.43
found θ with arctan(4m/10m) = 21.8°
moving the origin onto the point on the forces I then used component tree to solve for the y-direction where
Ft*sin(21.8)+Ft*sin(21.8)-Fg=0,
and ignored x since they would cancel out.

the answer I got was Ft = 39.623N
when I work in reverse the magnitude gives me the correct #s and everything adds to 0.

It's been a long time since I've done this kind of physics so maybe I'm missing something dumb here. But I can't find it.
 
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Seems fine to me. Why do you think there is a problem?
 
It is an online problem so it gives feedback and apparently this is an incorrect answer.
 
Some automated answer checkers will be very particular about what type of answers they accept. Minor things such as the number of decimals, the value of g that you use, or rounding errors can play a role in this.
 
Thanks I got it apparently I had to use exactly 9.8 for gravity.
 

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