In the PIM calculation T = D(60)/S, what are the units of S?

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Multiple Choice

In the PIM calculation T = D(60)/S, what are the units of S?

The key idea is that to get a time from distance and speed you divide distance by speed, so the distance and speed units must line up to give a time unit. D(60) represents the distance covered in 60 seconds (one minute), so its unit is nautical miles. To obtain time in hours from D(60), the speed S must be in nautical miles per hour (knots). In that case T comes out in hours (for example, D(60) = S/60 nautical miles, so T = (S/60)/S = 1/60 hours, which is one minute). Therefore the unit of S is nautical miles per hour, i.e., knots; among the options, Nautical Miles is the representative unit.

The key idea is that to get a time from distance and speed you divide distance by speed, so the distance and speed units must line up to give a time unit. D(60) represents the distance covered in 60 seconds (one minute), so its unit is nautical miles. To obtain time in hours from D(60), the speed S must be in nautical miles per hour (knots). In that case T comes out in hours (for example, D(60) = S/60 nautical miles, so T = (S/60)/S = 1/60 hours, which is one minute). Therefore the unit of S is nautical miles per hour, i.e., knots; among the options, Nautical Miles is the representative unit.

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