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Pictured here is the University of Manitoba Center for Earth Observation Science's air/ice boat "Skippy" (photo courtesy CEOS). Skippy has a large fan at the back to allow it to accelerate as it slides across icy surfaces. Suppose you are piloting a similar craft on very slippery ice which will not slow the boat at all if it is coasting. Suppose also that the fan on your boat can be reversed instantanously, switching its direction of thrust from forward to backward. Assume the action of the fan (when it is on) always produces an acceleration with the same constant magnitude. Air resistance is negligible.
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