Question 59Navigation Problems70% to pass
If the speed necessary for reaching port at a designated time is 17.4 knots and the pitch of the propeller is 25.6 feet, how many revolutions per minute will the shaft have to turn, assuming a 3% positive slip?
AI Explanation
The correct answer is D) 71 revolutions per minute.
To calculate the revolutions per minute (RPM) of the shaft, we need to use the formula: RPM = (Speed in knots x 1.6889) / (Propeller pitch in feet x (1 - Slip percentage)).
Given:
- Speed necessary for reaching port: 17.4 knots
- Propeller pitch: 25.6 feet
- Positive slip: 3%
Plugging the values into the formula:
RPM = (17.4 x 1.6889) / (25.6 x (1 - 0.03))
RPM = 29.4 / 0.412
RPM = 71
The other answer choices are incorrect because they do not correctly apply the formula and account for the given propeller pitch and positive slip.
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