Check my vector work for exam practice

  • Thread starter phunphysics2
  • Start date
  • Tags Tags
    Vector Work
3 replies · 2K views · last reply
phunphysics2
Messages
29
Reaction score
0
Greetings fellow Physics adorers,

I was wondering if someone could please check my work for this problem. I attached pictures of my work and the problem. It involves vectors.


My instructor said we will be having a problem like this on our exam, and it is an even problem so I'd definitely like to know if I am okay for this problem or not. Thanks for all the help!
Handwritten whiteboard work resolving four vectors P, Q, R and S into x and y components using sine and cosine, with the sum x = 11.13 and y = 2.74 leading to a resultant magnitude and angle.


Textbook problem 26, The Sum of Four: find the sum of four vectors in (a) unit-vector notation and (b) magnitude and (c) angle relative to +x. P: 10.0 m at 25.0° counterclockwise from +x; Q: 12.0 m at 10.0° counterclockwise from +y; R: 8.00 m at 20.0° clockwise from -y; S: 9.00 m at 40.0° counterclockwise from -y.
 
If I decipher your handwriting correctly, you have determined the absolute angles to be 25, 100, 250 and 320 degrees. The last one is wrong. Observe that "-y" corresponds to 3 x 90 = 270 degrees, 40 degrees counterclockwise from -y would be 270 + 40 = 310 degrees.
 
Greetings Voko,

Thank you VERY much for your response. And yes I do certainly see why that should be 310 degrees and NOT 320 degrees. Other than that, do you think my work looked reasonably well? Was I on the right track to solvong it other than that angle error? I apologize for the handwiriting. I will try to write bigger and cleaner next time.
 
The components of the first three vectors are calculated correctly. As far as I can tell, you then sum them component-wise, thus getting the components of the resultant vector, then you determine its magnitude and angle. All that seems correct.