Calculating Work Done by a Steady Wind in a Given Direction

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Homework Help Overview

The discussion revolves around calculating the work done by a steady wind on a person walking in two different directions. The problem involves forces, angles, and displacement in a physics context, specifically focusing on the concepts of work and vector components.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the correct interpretation of angles in relation to the force of the wind and the displacement of the person. Questions arise regarding the angle definitions and the use of free body diagrams to analyze the situation.

Discussion Status

Participants are actively discussing the angles involved in the problem and how to apply them to calculate work done. Some have provided guidance on using free body diagrams and clarifying the relationship between the force and displacement vectors. There is an ongoing exploration of how to accurately represent the angles based on the problem's wording.

Contextual Notes

There is mention of potential confusion regarding the definition of angles, particularly the phrase "30 degrees east of north," which is being clarified through discussion. Participants are also addressing the need for accurate labeling in diagrams to avoid misinterpretation.

Sneakatone
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a strong steady wind provides a force of 170 N in a direction 30 degrees east of north on a person. If the person walks first 110 m north and then 190 m east what is the total work done by the wind?

I used W=FDcosθ
170(110)cos(30)=16194.67J
170(190)cos(30)=27972.62

should 110 m north be 90 degrees?
 
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Sneakatone said:
should 110 m north be 90 degrees?

Yes, you can take north to mean 90 degrees, but that is 90 degrees from the positive x-axis. So, if you do that, then you have to take all of your angles from the positive x-axis.

What you want for your θ is the angle between the Force and the displacement. You have two displacement vectors.

What is the angle between the first "walk" and the force of the wind. And what is the angle between the second "walk" and the wind.
 
would this picture be right?
 

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I would do 2 free body diagrams. Think of the this as two problems. "How much work is done by the wind during your 110m walk?" and "How much work is done by the wind on your 190m walk?"

You have the right idea in the orginal post. You just need to find the correct angles.
So, what are your angles?
 
sorry for the bad paint writing
 

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I attached a FBD for the first part. See what you can take from it and apply it to a FBD for the 2nd part. and Then find the work done in each instance.

Notice your problem says30 degrees due EAST of NORTH.
 
Sorry, here it is.
 

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the angle for part 2 is 60
 

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That looks good, assuming I'm looking at it right. I understand you're using paint do draw these so it's a little tough. Just be sure you're labeling everything correctly (see my diagram) when you draw them on your paper.

So what you do get for your work?
 
  • #10
170(110)cos(30)=16194.67J
170(190)cos(60)=16150 J
I added em and it was correct.
Thank you soo much again! I guessed I didnt not really know what east of north along with it surrounding angles ment until now.
 
  • #11
Yeah, wording can be tricky sometimes, just have to pay real close attention.
 

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