Problem 7-49 (b) Energy cons.

A river is flowing with a speed of $3.74\; m/s$ just upstream from a waterfall of vertical height $8.74\; m$. During each second $7.12\times10^4\; kg$ of water pass over the fall.

(a) [We will ignore this part]
(b) If there is complete conversion of gravitational potential energy to kinetic energy, what is the speed of the water at the bottom of the fall?

(Note: This is actually an unrealistic assumption; some of the energy in the fall will be converted into heat)

When the water is at the top of the fall it has (relative to the bottom):

(A)    $\text{Only } E_K$

(B)    $\text{Only } E_P$

(C)    $E_K + E_P$

(D)    $\text{No energy.}$