Acceleration in Two Dimensions of watercraft

[chudzoik]

Homework Statement

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?

Homework Equations

v_f = v_i + a * t
a = v / t
v = v₂ + (-v₁)
pythagoras and cosine law?

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.

 

[BruceW]

I think I need to separate the variables 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.

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.

 

[chudzoik]

But I don't think I have enough known variables to do that. If I use v_fx = v_ix + a_x * t then I don't have a_x 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.

 

[BruceW]

Yes, you do have a_x, 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.

 

[chudzoik]

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

 

[BruceW]

Yep. that's right