Question

Hello,
In Session 1: Vectors, the solution of the the problem 1A refers to a triangle where the net velocity is acting upward from its origin. I'm not getting why the net velocity would be working upward. Could someone point me in the right direction, please?

Answer 1

Are you asking about the problem of the rower at 6 mph rowing across a river with a current of 3 mph ?

Answer 2

velocity is a vector quantity, with both magnitude and direction.

In their solution, they assume "directly upward" (on the paper) is directly across the river, with the river flowing from left to right.

The idea is to add the two velocity vectors (rower + river current) so that the resultant vector is "straight across" the river.

Answer 3

Here is background on vectors
http://www.onlinemathlearning.com/adding-vectors.html
or see Khan's site
https://www.khanacademy.org/math/linear-algebra/vectors-and-spaces/vectors/v/adding-vectors

But the main idea is:
1) we have a vector for the current, for example <3, 0> (i.e. moves left to right at 3 mph)
2) we *want* a vector that points up (i.e. directly across the river) so <0, A>
(we don't know the length i.e. speed of this vector, but we do know it goes directly across the river)

3) we use "head-to-tail" addition to add the rowers vector, so that we create a resultant vector of <0,A>

Answer 4

the rower has a velocity vector of length 6 , but we can vary its direction.
Adding it to the river's velocity vector (head to tail) :