One knot is equal to 1.15077945 miles per hour. To convert knots into miles per hour, all you need to do is multiply the number of knots by 1.15077945. Therefore 140 knots is 140×1.15077945 or 161.109123 miles/hour TIME == = 0.1862091944 hours or 11.17255166 minutes or about 11 minutes and 10 seconds. Edwin