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Homework Help: Is the problem wrong (deals with resolving vectors into their components)?

  1. Jul 30, 2012 #1
    1. The problem statement, all variables and given/known data
    4.9b cites the y components to be sin degree and 4.9a is somehow cos degree for the x components (see picture)

    2. Relevant equations
    Here's a different textbook that supports my claim (see picture)


    3. The attempt at a solution
    Shouldn't the y components for problem 4.9b be cos instead of sin based on how the angle of the vector is oriented? Isn't this vice versa for problem 4.9a (this should be sin)
  2. jcsd
  3. Jul 31, 2012 #2
    When splitting a vector V, the y component is V*sinθ, and the x component is V*cosθ. It doesn't matter how the vector is oriented. The picture you posted from another textbook confirms what it shows in the first picture. If you rearrange the sin equation, you get V*sinθ=Vy (which is the y component of vector V)
  4. Jul 31, 2012 #3
    I just realized that T1 stood for vector V
    I thought that T1 somehow was identifying Vector y

    I feel stupid...REALLY stupid...
  5. Jul 31, 2012 #4
    Don't worry about it, I think physics makes everybody feel stupid. I'd like to point you to a quote by a great physicist, Richard Feynman.

    "When you are thinking about something that you don’t understand you have a terrible, uncomfortable feeling called ‘confusion’. It’s a very difficult and unhappy business. So, most of the time you are rather unhappy, actually, with this confusion. You can’t penetrate this thing. Now, is the confusion… is it because we are all some kind of apes that are kind of stupid working against this? Trying to figure out to put the two sticks together to reach the banana and we can’t quite make it? …the idea ? And I get that feeling all the time: that I am an ape trying to put two sticks together. So I always feel stupid. Once in a while, though, everything — the sticks — go together on me and I reach the banana.”
  6. Jul 31, 2012 #5
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