Simple vector problem

  • Thread starter Einstein
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  • #1
Einstein
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"simple" vector problem

I need help on the second part of this question:

The points A and B have position vectors (4i -11j +4k) and (7i +j +7k) respectively.

a) Find vector equation of the line passing through the two points in terms of a parameter t.

My answer: r = 4i -11j +4k + t(3i +12j +k)

b) Find the position vector of the point P on AB such that OP is perpendicular to AB where O is the origin.

I have attempted this many times but I do not know how to start. Can anyone please tell me how to. I am on the level capable of understanding scalar and dot product and converting vector equations into cartesian equations so i appreciate if you can keep it as simple as this (not too complex) and understandble. Thanks. By the way the answer to b) is 6i -3j +6k
 
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Answers and Replies

  • #2
arcnets
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Originally posted by Einstein
My answer: r = 4i -11j +4k + t(3i +12j +k)
Almost correct. Should read
r = 4i -11j +4k + t(3i +12j +3k)

For b), just remember that two vectors are perpendicular (orthogonal) WRT to each other, if their scalar product is zero.
 

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