NCERT Exercise 5.21 - Work, Energy and Power
Question: A windmill of swept area A faces wind speed v. Find airflow mass, its kinetic energy, and output for A=30 m², v=36 km/h, density=1.2 kg/m³, efficiency=25%.
Answer: Mass = **rhoAvt**; KE = **1/2 rhoAv³t**; electrical output = **4.5 kW**.
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