Question

A vector A is along the positive x axis .If B is another vector such that A×B is zero ,then B could be : a) 4j . b)-4j c) -( i+ j) d)(i+ k)

Answer 1

Given that
vector A is acting along X direction
That is
=

Also given

That is

as magnitude of a vector cannot be zero
So we can say that

Therefore angle between them is zero

Therefore also acting along x-axis

If the cross productof two vectors is zero it implies that the vectors are either paralell or anti-paralell

you see the cross product of two vectors A and B is given by

|A| |B| sin theeta when theeta becomes 0 or 180 degrees sin of theeta will be zero

so there is no such option
Dear student i think your options have some mistake

Thank you