Gr12 Energy Prob: Solving for Waterfall Speed at Top

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Homework Statement


"The highest waterfall in Canada is Della Falls in B.C., with a change in elevation of 4.4*10^2m. When the water has fallen 12% of its way to the bottom, its speed is 33 m/s. Neglecting air resistance and fluid friction, determine the speed of the water at the top of the waterfall."

RTF: V1
V2 = 33 m/s

(need help on this part, tell me if I'm doing it right) I pick the ground as a point of reference, so:
y1 = 4.4*10^2 m
y2 = (4.4*10^2)(1-0.12)

Homework Equations



Et1=Et2 (Conservation of Energy)

The Attempt at a Solution



Et1=Et2
1/2mv1^2 + mgy1 = 1/2mv2^2 +mgy2
(mass cancels out)
v1 = sqrt( 2 ( 0.5v2^2 + g(y2-y1)))

I plug everything in and I get 7.4 m/s, book says 5.0 m/s
 

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guess I'm right then? Thanks