Question
Q A VECTOR A POINTS VERTICALLY UPWARD & B PTS. TOWARDS NORTH. VEC. PRODUCT ACROSS B IS ALONG WHICH DIRECTION?
Q LET < B/W TWO NON ZERO VECTORS A & B BE 120* & ITS RESULTANT BE C THEN
1) C MUST BE EQUAL TO MOD. OF A-B
2) C MUST BE LESS THAN MOD. OF A-B
3)C MUST BE GREATER THAN MOD. OF A-B
4)C MAY BE EQUAL TO MOD. OF A-B
Joshi sir comment
Take your right hand fingers along A and curl these fingers along B, thumb will give you an idea for A × B. for the given problem answer will be west.
|A+B|2 = |A|2 + |B|2+ 2A.B (1)
|A-B|2 = |A|2 + |B|2 - 2A.B (2)
on subtracting (2) by (1)
|A+B|2 - |A-B|2 = 4A.B
so C2 = |A-B|2 + 4A.B
or C2 = |A-B|2 +4|A||B|cos120
since cos120 is negative so C will be less than |A-B|