Gravitational Potential Energy of a rope

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Homework Help Overview

The problem context involves calculating the speed of a person swinging on a rope, specifically focusing on gravitational potential energy and its conversion to kinetic energy. The scenario includes a rope length of 10.0 meters and an initial angle of 35 degrees with the vertical.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply the work-energy principle, expressing gravitational potential energy in terms of height changes and relating it to kinetic energy. They express uncertainty about their setup and calculations.

Discussion Status

Some participants question the original poster's concerns about their setup, suggesting that there may not be an issue with the approach taken. There is an indication that computational errors may have occurred, and participants are encouraged to share calculations for further examination.

Contextual Notes

The original poster mentions issues with a homework submission website not accepting their answer, which raises questions about potential rounding errors or computational mistakes in their calculations.

FailingPHYS
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The problem states that: "Bruce stands on a bank beside a pond, grasps the end of a 10.0m long rope attached to a nearby tree and swings out to drop into the water. If the rope starts at an angle of 35 degrees with the vertical, what is Bruce's speed at the bottom of the swing?
Variables:
angle of the rope with the vertical: 35 degrees
Length of rope: 10m


I'm trying to use the equation for the change in gravitational potential energy, where the Work due to gravity = -mg(yf-yi) which is equal to Kf-Ki, and therefore -mg(yf-yi)= -1/2mvi^2+-1/2mvf^2. With the initial velocity as 0 and the masses canceling out the solution should be Vf=\sqrt{}2g(yf-yi).



I am apparently either setting up the question wrong, or going about it wrong all together. I'm pretty much stumped as to what I'm doing wrong and how to fix it. If someone could point me in the right direction I'd be ecstatic...
 
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There is nothing wrong with your setup. Why do you think that there is?
 
I thought I was doing it right, but the website we use to submit our homework wasn't accepting the answer I got from the formula. Thanks.
 
FailingPHYS said:
I thought I was doing it right, but the website we use to submit our homework wasn't accepting the answer I got from the formula. Thanks.

You must be making a computational error. If you post your calculations, we can find your mistake.
 
That's okay. I think I know what happened. I probably rounded off to the wrong number is all. A similar thing happened in another homework assignment after I posted the question. Thankfully I caught that one before I ran out of chances to answer the question.
 

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