Finding Magnitudes of Forces in Similar Triangles

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Homework Help Overview

The discussion revolves around determining the magnitudes of forces in a physics problem involving vectors and angles. The original poster presents a scenario with two forces, one known and the other unknown, and seeks to find their magnitudes based on the resultant force's angle.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the use of scale diagrams to visualize the forces and their resultant. There are questions about how to proceed without knowing the second force's magnitude and suggestions to use trigonometry to find the sides of the triangle formed by the forces.

Discussion Status

Participants have engaged in exploring different methods to approach the problem, including sketching vectors and considering the properties of similar triangles. There is an ongoing dialogue about the relationship between the angles and sides of the triangle, but no consensus has been reached on a specific method or solution.

Contextual Notes

There is an emphasis on the requirement to find an algebraic answer, which may influence the approach taken by participants. The discussion also highlights the challenge of drawing to scale without knowing the second force's magnitude.

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An upward force of magnitude 30N is combined with a second force F which makes an angle of 10degree with the horizontal. The resultant makes an anglre of 40degree with the horizontal.

a. Determine the magnitude of the second force
b. Determine the magnitude of the resultant
 
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Where is your attempt?
 
rpthomps said:
Where is your attempt?
I have no idea how to do it
 
I would start with a sketch of the vectors.
 
IN fact if you make a good scale diagram, you could answer the question pretty closely and I think it would give you a good feel for the algebraic approach,
 
rpthomps said:
IN fact if you make a good scale diagram, you could answer the question pretty closely and I think it would give you a good feel for the algebraic approach,

Ok this is my diagram. Then what?
 

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Well, if you made it to scale, you could just measure the lines now and that would be your answer. But if you are required to come up with an algebraic answer perhaps some trig can help you here. Can you think of some trigonometry that could help you find the sides of that shape?
 
rpthomps said:
Well, if you made it to scale, you could just measure the lines now and that would be your answer. But if you are required to come up with an algebraic answer perhaps some trig can help you here. Can you think of some trigonometry that could

help you find the sides of that shape?

How can i draw to scale if i don't know the 2nd force?
 
By using a protractor. :)
 
  • #10
Wh
rpthomps said:
By using a protractor. :)

What about the length of 2nd force? The magnitude is yet to be calculated
 
  • #11
As long as the angles in the triangle are all the same, it doesn't matter what the size of the triangle is, it will be similar to a triangle that I draw with the exact same angles. If I know one side, then I use a scale, we will get the same answer for the lengths. That's the "magic" of similar triangles.
 

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