Differentiate between gravitational potential energy and electric potential energy.
A body of mass $m$ moves vertically through a distance $h$ close to the Earth’s surface. Use the definition of work done to derive an expression for the change in the body’s gravitational potential energy.
Water moves down a stream from a reservoir and then makes a water wheel turn, as shown in Fig. 4.1. While the water drops through a vertical height of $120\,\text{m}$, gravitational potential energy changes into other forms of energy, including the water’s kinetic energy. By the time the water reaches the wheel, its kinetic energy is only $10\%$ of its gravitational potential energy at the reservoir. Show that the water’s speed on reaching the wheel is $15\,\text{m s}^{-1}$.
The spinning water wheel is used to generate $110\,\text{kW}$ of electrical power. Determine the mass of water flowing each second through the wheel, if the conversion of the water’s kinetic energy into electric energy is $25\%$ efficient.
The spinning water wheel is used to generate $110\text{ kW}$ of electrical power. Determine the mass of water flowing each second through the wheel, if the conversion of the water’s kinetic energy into electric energy is $25\%$ efficient.