Cube sliding down with frictionless slide

[Nikou]

Homework Statement

A cube with m mass is released from the top of a slide, of h height, with a horizontal distance of d. [/B]

Homework Equations

Assuming there is no friction between the cube and the slide, ¿what is the minimal information i need to calculate the speed of the cube at the end of the slide? [/B]

The Attempt at a Solution

I tried to solve it using the conservation of mechanical energy, so:[/B]

Initial mechanical energy = mgh
Final mechanical energy = (mv²)½
Therefore

mgh=(mv²)½
gh=(v²)½
2gh=v²
√2gh=v

So i only need to know g and h to solve this but the solution is not that, according to the website where i got this problem. The solution of the problem would be this:

We have this:

v²_f=v²_i + 2gΔx
(v²_i = 0 because at the beginning is static)

Where Δx is the displacement of the cube, therefore

v_f=√(2gΔx)

To find the value of Δx we use phytagoras theorem:

Δx=√(d²+h²)

So to calculate v_f we need to know d ,h, g

Why this solution is correct ,since mine requires less information?

(Sorry for my English, is not my first language)

 

[haruspex]

v²_f=v²_i + 2gΔx

The above appears to be taking the acceleration down the slope as g, but it will be less than that.
Your answer is correct, the website's wrong.

 

[Nikou]

Ok thank you! :D