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Foehammer
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Homework Statement
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Here are two displacements, each measured in meters:
A. 4i+5j-6k
B. -1i+2j+3k
What is the component of A that is perpendicular to the direction of B and in the plane of A and B.?
Homework Equations
The book gave me a hint to use this equation:
http://puu.sh/fFya9/3d102e2d2f.png
c being the magnitude of the result of A cross B. a and b being the magnitudes of vectors A and B.
The Attempt at a Solution
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I plugged the values into that:
c=(8.775)*(3.742)*sin(111.438)
c=30.564
I don't see how that is supposed to help me.
A cross B gives me the vector:
C=27i-6j+13k
This vector is perpendicular to the A,B plane.
Would I need to cross C by B again to get it back in the A,B plane? After doing that would I need to use this equation to find the final component part?
Doing that gives me:
D=-44i-94j+48k
A dot D=-934
-934=8.775*114.35*cos(phi)
phi=158.56
I think this is the angle between vectors A and D. Then is it just a*cos(158.56)
8.77*cos(158.56)=-8.17
I'm not 100% sure that is correct as I feel I messed up with being able to cross product twice to get back on the A,B plane. Your help is greatly appreciated.
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