What Is the Speed of Water at the Top of Della Falls?

[tamir102]

Homework Statement

The highest waterfall in Canada is the Della Falls in British Columbia, with a change
in elevation of 4.4  102 m. 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.

Homework Equations

E before = E after
1/2 mv^2 + mgh = 1/2 mv^2 + mgh
v^2 + 2gh = v^2 + 2gh
v^2 = v^2 + 2gh - 2gh
v = √v^2 + 2gh - 2gh

The Attempt at a Solution

GIVENS:

waterfall distance from ground = 440m
V2= 33m/s
water fallen at 12% distance = 387.2m


v = √v^2 + 2gh - 2gh
v = √(33m/s)^2 + 2(9.8 m/s^2)(387.2m) - 2(9.8 m/s^2)(440m)
v=7.35m/s


now the answer in the book is 5.0m/s and i was wondering what is the mistake that is made ?? or is the book just incorrect?


thank you for your help in advance..

 

[kuruman]

Start with kinetic + potential at 440 m is equal to kinetic plus potential at 387.2 meters. Use different symbols for the speed v and the height h. Your problem is you plugged the numbers in the wrong places because everything looks the same.

 

[tamir102]

thanks will work on it n message back

 

[cad]

thanks will work on it n message back

your answer 7.35 m/s is correct
the only reason it says 5.0 m/s in the book is because the book uses
10m/s for gravity because it is for easier calculations
thanks for helping me with a waterfall physics question

 

[tamir102]

i actually went to my physics teacher and he said the same thing you said cad.