A Levels Physics

The diagram shows a hydroelectric power station.
The reservoir is linked to the turbines by a pipe of uniform cross-sectional area. Water flows from
the reservoir, through the pipe and through the turbines at a constant rate.
reservoir
turbine house
Which statement about the change of energy of the water as it moves from X to Y is correct?
A It gains both gravitational potential energy and kinetic energy.
B
It loses gravitational potential energy and gains elastic potential energy.
It loses gravitational potential energy and gains kinetic energy.
D It loses both elastic potential energy and gravitational potential energy.
X.


Choice B is correct because:

Water is flowing downwards therefore its height from the surface is decreasing and hence its gravitational potential energy is also successfully decreasing. 

A successful change/conversion in energy is happening as the lost gravitational potential energy is converted into elastic potential energy. 

Choice A is incorrect because:

Water is flowing downwards therefore its height from the surface is decreasing and hence its gravitational potential energy is also decreasing.

Water cannot gain/lose kinetic energy as it is flowing at a constant rate.

Choice C is incorrect because water cannot gain/lose kinetic energy as it is flowing at a constant rate. 

Choice D is incorrect because:

Energy cannot be created or destroyed, it can only be converted from one form to another

From X to Y, the water is losing energy (gravitational potential energy & elastic potential energy) but not gaining any form of energy which means no change/conversion in energy is happening.

Work, Energy and Power | 2012 - O/N - 9702/13 | Q21