Swinging a Ball on a String: Who is Doing the Work?

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Homework Help Overview

The discussion revolves around the concept of work done by a force, specifically in the context of a ball attached to a string being swung in a circular motion. Participants are exploring whether the string does work on the ball and the implications of this in relation to the forces involved.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the definition of work and how it applies to the forces acting on the ball. There is confusion about whether the string or the hand is responsible for doing work on the ball, and some are seeking clarification on the relationship between force, displacement, and the angle involved.

Discussion Status

The discussion is ongoing, with participants attempting to clarify their understanding of the concept of work. Some guidance has been offered regarding the definition of work and the importance of the angle between the force and displacement, but there is no explicit consensus on the main question.

Contextual Notes

Participants express uncertainty about the definitions and formulas related to work, indicating a potential gap in their prior knowledge or resources. There is mention of a specific statement to evaluate as true or false, which adds a layer of complexity to their inquiry.

teres
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Homework Statement


If a ball is attached to a string and is swung in the air, does the string do the work on the ball?


Homework Equations



none

The Attempt at a Solution



I have tried to figure it out. I have thought that it did because the string was the force that made the ball swing but then I thought it was the hand holding the string that was doing the work. I am very confused about this and have been unable to find anything about it in my book.
 
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What is the definition of the work done by a force?
 
I am not sure what your reply means. Was it a question? Forgive me but I am out of my element in this class. I have no prior math other then algebra and formulas get me lost. I was not sure about the work done. The problem is a picture of a hand holding a string with a ball on it and is swinging it so the ball is moving in a circular motion. The statement is 'The string is doing work on the ball' We are to say if this is a true or false statement. I was not sure what force of energy it is and whether or not it was true. I looked in my book and my lecture notes but found no answers. If you can help I would greatly appreciate it.
 
Hi, teres

Homework help is provided on these forums. We try to guide you in the right direction so that you yourself can come up with the answer. We do not directly provide the answers.

The string does exert a force on the ball. In order to determine whether or not that force is doing work on the ball, you must go back to the basic definition of work. Is there a formula in your lecture notes that looks something like W = F(d)cos theta?? The key here is to determine the value of theta, which is the angle betweeen the force and the direction of the ball's displacement.
 
I have never seen this formula before. There has not been anything about the value of theta in our book. I wasn't asking for the answer, just some help in understanding it.
 
A force does work if there is a displacement of that force in the direction of its application. Does the string move in the direction of its tension force?
 

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