Work, Energy, and Power · Paper 2 — Free Physics SL Practice Questions

A wind turbine has blades of radius 35 m. The density of air is $1.2 \text{ kg m}^{-3}$. The wind speed is $12 \text{ m s}^{-1}$. The kinetic energy of air passing through the area swept by the blades per second is given by $\frac{1}{2}\rho A v^3$, where $\rho$ is the density of air, $A$ is the swept area, and $v$ is the wind speed. The turbine converts 40% of this kinetic energy into electrical energy per second.