Which unit is used to measure a ship's speed in nautical contexts?

• A. Knots
• B. Miles per hour
• C. Kilometers per hour
• D. Feet per second

Answer: (A)

In sea navigation, speed is expressed in knots because the distance used at sea is the nautical mile, and speed is measured as nautical miles per hour. A knot means one nautical mile traveled in one hour. So if a ship is moving at 20 knots, it covers 20 nautical miles in an hour. For context, one nautical mile is about 1.852 kilometers or 1.151 statute miles. Historically, sailors used a log line to measure speed by counting knots in a line as time passed, which gave rise to the term “knot” for speed at sea. Other units like miles per hour, kilometers per hour, or feet per second aren’t standard in nautical contexts because they don’t align with nautical miles and the navigation systems crews rely on.