Answer
No. Yes.
Work Step by Step
Two vectors add to zero if and only if they have the same length (magnitude) and point in exactly opposite directions.
On the other hand , 3 vectors of unequal magnitude CAN add to zero. For example, a vector 7 cm long pointing due east, added to two vectors of 4 and 3 cm pointing due west will give zero. In two or three dimensions, if the 3+ vectors, added tail-to-tip, gives a closed triangle, quadrilateral, or polygon, then the vector sum is zero.
