# Acceleration in Two Dimensions

1. Jan 29, 2012

### chudzoik

1. The problem statement, all variables and given/known data
A watercraft with an initial velocity of 6.4 m/s [E] undergoes an average acceleration of 2.0 m/s2 for 2.5 s. What is the final velocity of the watercraft?

2. Relevant equations
vf = vi + a * t
a = v / t
v = v2 + (-v1)
pythagoras and cosine law?

3. The attempt at a solution

I think I need to separate the velocities into x and y components and calculate the final velocity in both the x and y components to find the final velocity, but I don't know if that's correct. To be honest I don't really know where how to start the question.

Last edited: Jan 29, 2012
2. Jan 29, 2012

### BruceW

Yep, that's how you should do it. You've got the x acceleration and y acceleration, and so you can solve the equations of motion for each coordinate separately.

3. Jan 29, 2012

### chudzoik

But I don't think I have enough known variables to do that. If I use vfx = vix + ax * t then I don't have ax and I don't have the initial velocity in the y direction either so I can't figure out the final velocity in the y direction.

4. Jan 29, 2012

### BruceW

Yes, you do have ax, because the question says that the acceleration is only in the south direction.
And you do know the initial velocity in the y direction, because the question says that the initial velocity is purely to the east.

5. Jan 29, 2012

### chudzoik

So they are both 0 then? I think that clears up a lot of my confusion with this problem.

6. Jan 30, 2012

### BruceW

Yep. that's right