While steaming at 15.0 knots, your vessel consumes 326 barrels of fuel oil per day. In order to reduce consumption to 178 barrels of fuel oil per day, what is the maximum speed the vessel can turn for?
ā¢ Relationship between fuel consumption and speed for displacement vessels (consumption changes with roughly the cube of speed) ā¢ Setting up a ratio or proportion between the known speed/consumption and the unknown speed/new consumption ā¢ Careful unit handling: barrels per day stays the same unit, only the numbers change
ā¢ If fuel consumption is roughly proportional to the cube of the speed, how can you relate the first condition (15 knots, 326 bbl/day) to the second condition (unknown speed, 178 bbl/day)? ā¢ How can you rearrange the proportionality so the unknown speed is on one side and everything else (known speed and consumptions) is on the other? ā¢ After you compute the new speed, which choice is numerically closest to your calculated value?
ā¢ Write an equation showing consumptionā / consumptionā = (speedā / speedā)Ā³ before doing any arithmetic ā¢ Be sure you are solving for speedā, not fuel consumption ā¢ After calculating, compare your result carefully with each multiple-choice option and check for rounding or calculator errors
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