Why is there no acceleration in the southern/y direction?

[yashboi123]

Homework Statement

A river flows due south with a speed of 2.5 m/s. You steer a motorboat across the river; your velocity relative to the water is 5.2 m/s due east. The river is 650 m wide.

How far south of your starting point will you reach the opposite bank?

Relevant Equations

Δ x = v 0 t + 1 2 a t 2
v = v 0 + a t
Δ x/ Δt = v

The correct answer is obtained by rearranging Δ x/ Δt = v. However, I assumed there would be some acceleration in the y direction so I tried to use the kinematic equations. To find the time I simply rearranged Δ x/ Δt = v, assigning v=5.2 m/s and Δ x = 650. I assumed there is no acceleration in the x/east direction, but why is there no acceleration in the y/southern direction?

 

[Frabjous]

Think about what “velocity relative to the water” means.

 

[yashboi123]

so essentially relative to water means that speed is constant, in turn causing there to be no acceleration for the east direction. But why can we just assume the river has no acceleration?

 

[DaveC426913]

But why can we just assume the river has no acceleration?

Because the problem statement says that the river flows at a speed of 2.5m/s.
That implies an acceleration of 0.

Also, you're not given a value for acceleration, so if you aren't going to assume zero, what value would you assume?

 

[yashboi123]

I see, thank you.

 

[yashboi123]

Because the problem statement says that the river flows at a speed of 2.5m/s.
That implies an acceleration of 0.

Also, you're not given a value for acceleration, so if you aren't going to assume zero, what value would you assume?

Haha I thought we would have to find the acceleration ourselves then solve

 

[hmmm27]

Why do you keep saying "acceleration" ?

 

[yashboi123]

Why do you keep saying "acceleration" ?

What else should I say.

 

[hmmm27]

What else should I say.

Something relevant to the question, which has nothing that implies an acceleration.

 

[yashboi123]

That's why I asked the question

 

[hmmm27]

So, what do you see as implying the need for an "acceleration" ?