A red car is driving west at 35mph and a blue car drove east at 49mph. What is the difference in velocity?
When applying direction to these numbers while removing east and west, you will be left with one car driving -35mph and the other driving 49mph. To find the difference, you subtract 49 from -35 or -35 from 49, depending on the relevance being placed on which car. The magnitude would be -84mph or 84mph. My teacher, however, is telling the class that the magnitude of difference of velocity is 14mph. I tried to explain it to him, but my explanations seem to beand he's misleading the class

Question

A red car is driving west at 35mph and a blue car drove east at 49mph. What is the difference in velocity? 
When applying direction to these numbers while removing east and west, you will be left with one car driving -35mph and the other driving 49mph. To find the difference, you subtract 49 from -35 or -35 from 49, depending on the relevance being placed on which car. The magnitude would be -84mph or 84mph. My teacher, however, is telling the class that the magnitude of difference of velocity is 14mph. I tried to explain it to him, but my explanations seem to beand he's misleading the class

deepolisnoob · Answer

Continuation of question: I tried to explain it to him but my explanations seem to be inefficient. He's misleading the class. Could someone tell me of another way to explain this situation that may show him he's wrong? Or if I'm wrong, please tell me where I went wrong.

anonymous · Answer

Did you study vectors yet?

anonymous · Answer

Velocity is a vector.
When you draw one vector, you continue the second one from the head of the first one.

anonymous · Answer

|dw:1411424705191:dw|