# Relative Motion in Water

1. Jul 7, 2009

### dance_sg

1.A girl can swim 4.5m/s. If she tries to swim across a river flowing at 3.8m/s, what is her resultant velocity?

2. cosine, sine, tangent, v=vf -v i

3. would i just subtract 3.8m/s from 4.5m/s in order to find the velocity?

2. Jul 7, 2009

### RoyalCat

Note, she is swimming ACROSS a river, not against the stream.
$$\vec V_{12}= \vec V_1-\vec V_2$$

3. Jul 7, 2009

### dance_sg

So you would add the two numbers rather then subtract them??

4. Jul 7, 2009

### dance_sg

oh oops. i meant to say that i would subtact 4.5 from 3.8 instead and it would be negative?

5. Jul 7, 2009