Answer to Question #133129 in Physics for Elvis

Question

State five uses of solar energy to man.

A lake is 10m deep and 1km by 1km in area. All the water goes over a waterfall 300 m high. How much electrical energy is produced at 100% efficiency from this energy supply?

Answer 1

Five uses of solar energy to man:

1) use solar energy to produce electrical energy

2) use solar energy to produce thermal energy

3) use solar energy to produce mechanical energy (for example first converting it to thermal energy)

4) use solar energy for planting trees and plants

5) use solar energy for chemical reactions (some reactions such as photosynthesis only occur in the presence of light)

Calculate the volume of water:

$$V=abc.$$

The mass of this water is

$$m=\rho V=\rho abc.$$

With 100% efficiency, the entire potential energy will be converted to electrical energy:

$$E=mgh=\rho abcgh,\\ E=1000\cdot10\cdot1000\cdot1000\cdot9.8\cdot300=\\=2.94\cdot10^{13}\text{ J}.$$