Question

17. A vector A points vertically upward and B points
towards north. The vector product Ax B is :-
(1) null vector
(2) along west
(3) along east
(4) vertically downward​

Answer 1

17. A vector A points vertically upward and B points

towards north. The vector product Ax B is :-

(1) null vector

(2) along west

(3) along east

(4) vertically downward

__________________________

1. Null vector or zero

______________________________________

Lets A, B & n as vectors.  

A is pointing upwards. B is pointing north, which is also upwards.  

Vector product is given by:-

A x B = |A| |B|Sin θ x n  

where n is a vector perpendicular in the direction of both A & B.

Angle θ between A & B is zero, as A & B both are parallel to each other.  

A  x B = |A| |B|Sin 0  = 0

Hence vector product of vector A & vector B is zero.

Answer 2

U can use the right hand thumb rule to do it.Draw the vectors or u may hv to imagine little straighten ur palm n place it on the the first vector in the cross product i.e. A now roll ur fingers towards the B vector, the dirction in which ur thumb is pointing will the the direction of the cross product vector.its kind of messy answer so check in u tube once the right hand thumb rule n apply it as i tld.