You are underway on course 254°T at a speed of 16.5 knots. You sight a rock bearing 255°T at a radar range of 6.1 miles at 0916. If you change course at 0922, what is the course to steer to leave the rock abeam to starboard at 1.5 miles?
• Relative motion of own ship toward the rock between 0916 and 0922 • Using time, speed, and distance to find how far you travel before altering course • Constructing or visualizing a right triangle of clearance so that the rock ends up abeam at 1.5 miles
• From 0916 to 0922, how many minutes pass, and how many miles do you travel at 16.5 knots in that time? • After you advance your own-ship position to 0922, what line from the rock represents the rock being abeam to starboard at 1.5 miles? How does your new course relate to that line? • Which of the answer choices gives a track that would pass the rock on your starboard side, not port, at the required distance?
• Be sure to convert minutes to hours correctly when using speed in knots • Confirm your advanced position from 0916 to 0922 before drawing or imagining any new course line • Check that your final course makes the rock lie 90° on your starboard beam at the closest point of approach and at 1.5 miles
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