A wind turbine has blades, which sweep out a circular area.
The wind is blowing directly towards the turbine at a speed of 10 m/s10\text{ m/s}10 m/s. At this wind speed, 9000 kg9000\text{ kg}9000 kg of air passes every second through the circular area swept out by the blades.
Calculate the kinetic energy of the air travelling at 10 m/s10\text{ m/s}10 m/s, which passes through the circular area in 1 s1\text{ s}1 s.
The turbine converts 15%15\%15% of the kinetic energy of the wind to electrical energy. Calculate the electrical power output of the turbine. State any equation that you use.
On another day, the wind speed is half that in (a).
Calculate the mass of air passing through the circular area per second on this day.
Calculate the power output of the wind turbine on the second day as a fraction of that on the first day.
533 exam-style questions on CIE IGCSE Physics 1.7 Energy, work and power, covering 1.7.1a Energy stores and energy transfers, 1.7.1b Conservation of energy, 1.7.1c Kinetic and gravitational potential energy, 1.7.2 Work done, 1.7.3 Energy resources, 1.7.3a Energy resources and electricity generation, 1.7.3b Nuclear fusion as an energy source, 1.7.3c Efficiency of energy transfer, and 1.7.4 Power. Each one has a worked solution and a mark scheme showing where the marks go.