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Horsepower of an Ox

In many countries, oxen, guided by children, plow straight, level furrows through soil. The ox of the figure pulls its plow a length of 200 meters in five minutes.

Calculate the least average horsepower expended by the ox.
♦  We have no way of knowing what friction force occur. To ignore friction is a major assumption. We ignore friction; our answer will be a "least power required." As system, we take the soil removed from the furrow once the ox completes a furrow. The mass of soil tilled equals:


Ignoring friction, the Extrinsic Energy Equation applies:

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