How Can Mary Row Across a Flowing River?

[osker246]

Homework Statement

Mary needs to row her boat across a 100 m wide river that is flowing to the east at a speed of 1.0 m/s. Mary can row the boat with a speed of 2.0 m/s relative to the water.

Homework Equations

pythagorean theorem: a^2+b^2=c^2

The Attempt at a Solution

Ok so I know this is pretty straight forward problem. But the 100 m is throwing me off here. I draw a vector diagram and add the two component vectors:

(1,0)
+(0,2)
------
(1,2)

Now i used pythagorean theorem to find the resultant 1^2 + 2^2 = R^2, in which R=5^1/2=2.2. So she's moving across the river at a rate of 2.2 m/s. Now I'm not sure how 2.2 m/s and 100 m finds her displacement. Any tips?

 

[osker246]

never mind got it figured out.