ISRO 2007- ECE Vectors

Question

A unit vector perpendicular to the vectors a= 2i –3j + k and b=i+j-2k , is

a)  (1/ √ 3 ) (–i+j+k)

b) (1/ √ 3 )(i+j- k)

c) (1/ √ 3 )(i + j+k)

d)  (i+j+k)

Comments

Vectors were not in GATE syllabus ! and moreover this ques. is from ECE branch! can u pls share what to prepare in Eng.maths apart from GATE syllabus?

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I shared this for to prepare for ISRO not GATE. Some topics are common in ECE and CSE question for ISRO , only that questions I shared. Vectors were part of Btech syllabus, so we cannot blindly say that will not be asked.
Moreover in ISRO some topics like Neural networks are also asked in some years

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yeah , that's what my question !can u share that common part which is shared by ECE and CSE?

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Digital Logic, some part of computer networks (mainly physical and data link layer) computer architecture and Mathematics.

You can correlate them while going through ECE Question paper

Answer 1

For vector to be perpendicular their dot product should be 0. Cehck each option only C) and D) when undergo dot product with given two vectors gives 0.

Dot product of two vectors xi + yj + zk and ai + bj + ck is given by ax + by + cz.

Now a unit vector is the one that is divided by its magnitude. It means for a given vector when we divide it by its magnitude we get unit vector.

So the vector that will be perpendicular is i+j+k and its magnitude is √3 so answer is option C).

Comments

answer is correct but Dot product should be zero for perpendicular vectors.. because a.b = |a| |b| cos 90°.. so a.b = 0

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Yes my mistake, corrected now.