Question 115Navigation Problems70% to pass
If the speed necessary for reaching port at a designated time is 16.8 knots and the pitch of the propeller is 22.3 feet, how many revolutions per minute will the shaft have to turn, assuming a 4% negative slip?
AI Explanation
The correct answer is B) 73 revolutions per minute.
To arrive at this answer, we need to use the formula for propeller revolutions per minute (RPM):
RPM = (Speed in knots x 1.688) / (Propeller pitch in feet x (1 - Slip percentage))
Given information:
- Speed required: 16.8 knots
- Propeller pitch: 22.3 feet
- Slip percentage: 4% (or 0.04)
Plugging these values into the formula:
RPM = (16.8 x 1.688) / (22.3 x (1 - 0.04))
RPM = 28.3 / (22.3 x 0.96)
RPM = 28.3 / 21.408
RPM = 73 (rounded to the nearest whole number)
The other options are incorrect because they do not correctly apply the formula or account for the given 4% negative slip.
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