Pressure of the Wind.
Air pressure is a big factor in the matter of aeroplane horsepower. Allowing that a dead calm exists, a body moving in the atmosphere creates more or less resistance. The faster it moves, the greater is this resistance. Moving at the rate of 60 miles an hour the resistance,
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Miles per Hour | Horse Power per sq. foot |
10 | 0.013 |
15 | 0.044 |
20 | 0.105 |
25 | 0.205 |
30 | 0.354 |
40 | 0.84 |
50 | 1.64 |
60 | 2.83 |
80 | 6.72 |
100 | 13.12 |
While the pressure per square foot at 60 miles an hour, is only 1.64 horsepower, at 100 miles, less than double the speed, it has increased to 13.12 horsepower, or exactly eight times as much. In other words the pressure of the wind increases with the square of the velocity. Wind at 10 miles an hour has four times more pressure than wind at 5 miles an hour.