• # question_answer The vector that must be added to the vector $\hat{i}-3\hat{j}+2\hat{k}$ and $3\hat{i}+6\hat{j}-7\hat{k}$ so that the resultant vector is a unit vector along the y­­-axis is A)            $4\hat{i}+2\hat{j}+5\hat{k}$ B)                                      $-4\hat{i}-2\hat{j}+5\hat{k}$ C)            $3\hat{i}+4\hat{j}+5\hat{k}$                                          D)  Null vector

Unit vector along y axis $=\hat{j}$ so the required vector $=\hat{j}-[(\hat{i}-3\hat{j}+2\hat{k})+(3\hat{i}+6\hat{j}-7\hat{k})]$$=-\,4\hat{i}-\,2\hat{j}+5\hat{k}$