7-49(b).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 7.12X104 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)

 
Correct!

If all potential energy is converted to kinetic energy then:
 

 

(A) (EK + EP)top = (EP)bottom

(B) (EK + EP)top = (EK)bottom

(C) (EK + EP)top = (EK + EP)bottom