Your company wants to know at what time you will be arriving at the fleeting area at Sycamore Chute Light (mile 740.3 AHP) in Memphis, TN. You are making turns for 9.0 mph and you estimate the average current at 2.2 mph. Figuring the distance and time from Hole in the Wall Lt. (mile 373.4 AHP), what is your ETA at Sycamore Chute Lt.?
• Use Speed = Distance / Time to find how long the trip takes • Remember speed over ground is affected by current (vessel speed vs. current speed) • Understand what the river miles "AHP" mean so you know if you’re going with or against the current
• First decide if your actual speed over the ground is your engine speed plus the current or minus the current, based on the river miles and current direction • Compute the total distance between the two river miles, then divide by your speed over ground to get total hours underway • Convert the decimal hours into hours and minutes and add that to your departure date/time, watching for day changes
• Be sure you used miles per hour (mph) consistently with river miles (no knots or nautical miles here) • Double‑check whether you subtracted or added the current to get speed over ground • After adding travel time to the departure time, confirm the correct date change before choosing among April 19th times
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