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The speed of a vessel relative to the fluid in which it travels is often measured in knots. The term comes from the practice of throwing a wooden break (chip log) behind a boat connected to a rope with knots at intervals of a little over 14 meters. The number of knots of rope released in about 30 seconds would indicate the speed of the vessel. In still water or air, a knot is equal to a nautical mile (roughly a minute of latitude) traveled in one hour, exactly 1.852 km/h. Typical walking speed is 2 knots. The beaufort wind force scale, developed by Sir Francis Beaufort in 1805, measured the qualitative wind effect upon sails. One hundred years later the scale was used to describe the conditions at sea, land, and trees, rather than sails. |
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| knots | km/h | mph | m/s | ||
|---|---|---|---|---|---|
| 0.54 | 1.00 | 0.62 | 0.27 | ||
| 0.87 | 1.61 | 1.00 | 0.45 | ||
| 1.00 | 1.852 | 1.15 | 0.51 | ||
| 1.94 | 3.60 | 2.24 | 1.00 | ||
| knots | km/h | mph | m/s | Beaufort number | Wind description |
| 0 | 0 | 0 | 0 | 0 | Calm |
| 1 | 1 | 1 | 0.3 | 1 | Light air |
| 4 | 7 | 4 | 1.6 | 2 | Light breeze |
| 7 | 12 | 8 | 3.4 | 3 | Gentle breeze |
| 11 | 20 | 13 | 5.5 | 4 | Moderate breeze |
| 16 | 30 | 19 | 8.0 | 5 | Fresh breeze |
| 22 | 40 | 25 | 10.8 | 6 | Strong breeze |
| 28 | 51 | 32 | 13.9 | 7 | Near gale |
| 34 | 63 | 39 | 17.2 | 8 | Gale |
| 41 | 76 | 47 | 20.8 | 9 | Strong gale |
| 48 | 88 | 55 | 24.5 | 10 | Storm |
| 56 | 103 | 64 | 28.5 | 11 | Violent storm |
| 64 | 120 | 74 | 32.7 | 12 | Hurricane |
| knots | km/h | mph | m/s | Beaufort number | Wind description |
Comment (1)
Alex,
In case you missed this delightful cartoon of the Beaufort scale: http://www.howtoons.com/toon/the-beaufort-scale/
- j