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Vectors problem (part 2 with work)

  • Thread starter MarieWynn
  • Start date
  • #1
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Homework Statement


The diagram below shows two vectors, A and B, and their angles relative to the coordinate axes as indicated.
DATA: α= 47.5o β= 56.6o |A| = 7.9 cm. The vector A - B is parallel to the -x axis (points due West).
A) Calculate the y-component of vector B. Answer: -5.82 cm
B) Calculate the x component of the vector A - B .
C) Calculate the magnitude of the vector A + B.


Homework Equations


I.) Bx=B*cos(beta)
II.) By=B*sin(beta)
III.) Ax=A*cos(alpha)
IV.) Ax=A*sin(alpha)
V.) Cx=Ax+Bx

The Attempt at a Solution


The original problem doesn't give B, but does tell you that Ay=By, so you should be able to take By from the first part of the question and plug that value into equation II and solve for B, which allows you to use equation I to find Bx and then find Ax and add the two together to find the X component of vector A-B. The answer I came up with was 5.34 + -3.84 = 1.50. This is incorrect but I am not sure where I am going wrong. I've tried it a couple of different ways in case I was misunderstanding the meaning of A-B and all of the different ways to add those two together (or even subtract) are wrong.
 

Answers and Replies

  • #2
13
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Got past part 2 but not understanding why part 3 isn't correct. To find the magnitude of A+B you first have to find the X and Y components of B. Ax is 5.34. Ay is 5.82. Bx is -8.83 and By is -5.82. So when you use the pythagorean theorem to find C, you get the square root of [(5.34 + -8.83)2 + (5.82 + -5.82)2 ] which is 3.49. This answer is incorrect though. I've done the math over and over again but can't figure out where I am going wrong. Am I using the wrong formula?
 

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