Food energy converts to mechanical work. See how far that energy could actually push a box up a ramp — and how the angle changes the distance, but not the height.
Not to scale: the real distances involved are tens to hundreds of kilometres — far too long to draw. The animation shows a short, representative push; the numbers above are the real calculated values.
Simplification: 50% mechanical efficiency is a round number chosen to make the math easy to follow. Real human mechanical efficiency for sustained physical work is closer to 20–25% — most food energy becomes body heat, not useful work. Try lowering the efficiency slider to see how that changes the result.
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