Eg.1: A boat with a forward velocity in still water of 23 m/s is traveling across a river, directly towards the opposite shore. At the same time, a current of 8 m/s carries the boat down river. Determine the resultant velocity (ie: both magnitude and direction) of the boat. The Parallelogram Law for Adding Two Vectors a+ b 180 - 0 B To determine the sum of the two vectors a and b, complete the parallelogram formed by these two vectors when placed tail to tail. Their sum is the vector AD. the diagonal of the constructed parallelogram, a + b = AB + BD = AD