By Measurement This method requires you to draw a scale diagram representing the lengths and directions of the two vectors correctly to scale. Care must be taken to locate the two vectors at the correct angle to each other, and with the correct lengths, as given in the question. Using the scale chosen: 1 cm = 20 km/h, you can measure the sum vector's length. You can measure its angle with respect to the lower vector using a protractor. This method also works if the vectors are drawn tail-to-tail. This method will give an acceptable answer if careful measurements are made. BACK