Physics problem help --- area problem given watts, horsepower and efficiency?

Question

You are in charge of "solar-energizing" your grandfather's farm. At the farm's location, an average of 1.0 kW/m2 reaches the surface during the daylight hours on a clear day. If this could be converted at 28 percent efficiency to electric energy, how large a collection area would you need to run a 4.6 hp irrigation water pump during the daylight hours?

_____ m^2

Answer 1

Assuming the pump motor runs with 100% efficiency, 4.6 HP is 3.43 kw

1.0 kW/m² x .28 = 280 w/m²

3430 w / 280 w/m² = 12.25 m²

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