A wind turbine has blades that sweep an area of 2000 m2. It converts the power available in the
wind to electrical power with an efficiency of 50%.
What is the electrical power generated if the wind speed is 10 m s–1? (The density of air is
1.3 kg m–3.)

Question

A wind turbine has blades that sweep an area of 2000 m2. It converts the power available in the
wind to electrical power with an efficiency of 50%.
What is the electrical power generated if the wind speed is 10 m s–1? (The density of air is
1.3 kg m–3.)

anonymous · Answer

Find kinetic energy of the blade per unit time = power input = 1/2 m v^2 /t
They have given volume density  and area, which would give mass/ t
2000*10*1.3 = 26000J --------Power input = 1/2 * 26000 * (10)^2
= 1300kW

efficiency = power output/power input 
power output = 0.5*1300kw = 650kw