# Homework Help: Simple,quick relative velocity question?

1. Sep 9, 2009

### sameeralord

Hello I'll make it quick

Boat is travelling at 10m/s the sea is travelling at 5m/s. What is the speed of the boat relative to the sea and why?

Through vectors I worked it out to be 10m/s(not sure) but shouldn't it be five because if a person is standing in the sea and sees the boat it would be travelling at 5m/s.

The ship relative to the ground is 15m/s right.

Thank you!!

2. Sep 9, 2009

### rock.freak667

B=boat
S=Sea
G=ground.

B/S= Boat relative to Sea

I assume if there is a diagram it looks like this

--------> boat
----> sea

$$\vec{v}_{B/S}=\vec{v}_B-\vec{v}_S = 10-5=5 m/s$$

So the boat 'feels' as if it is traveling at 5m/s instead of 10m/s

3. Sep 10, 2009

### sameeralord

Thank you for your help. Isn't it 15m/s-10m/s. That is where my confusion lies. Isn't the boat relative to the ground 15m/s(someone in the shore would feel the boat travelling at 15m/s). When you are in the boat do you feel the resultant velocity or the actual velocity.

4. Sep 10, 2009

### Staff: Mentor

With respect to what? The water or the ground? And in what direction?
Presumably with respect to the ground.