Simple question - Statics

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


http://img11.imageshack.us/f/screenshot20110117at120.png/

The question is 2.3


Homework Equations


Law of cosines and law of sines.


The Attempt at a Solution



I used the law of cosines to find the resultant force. It is 139.1 lb. However, I get 113.1 degree for the direction of the resultant force. The textbook says that it is 67 degrees. I noticed that I get 67 degrees if I subtract 139.1 from 180 degrees. Why is this? Also, I am a little confused about significant figures. Why are they giving only two sig figs for the direction?

Thanks
 

Answers and Replies

  • #2
nvn
Science Advisor
Homework Helper
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Marioqwe: Usually you give the vector direction measured from a horizontal axis. Try that. They might be listing only two significant digits because the question asks you to determine the answer graphically, which is a less precise method than a calculator. Anyway, the correct answer is 67.0 deg, which rounds to the same answer.
 
  • #3
68
4
Thank You for your reply. It is more clear now.
 

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