If the speed necessary for reaching port at a designated time is 12.6 knots and the pitch of the propeller is 13.6 feet, how many revolutions per minute will the shaft have to turn, assuming no slip?
• Relationship between speed in knots, propeller pitch (feet/rev), and revolutions per minute (RPM) when there is no slip • Unit conversions: knots to feet per minute and how to handle time units correctly • Using the basic speed formula: ( \text{Speed} = \frac{\text{Distance}}{\text{Time}} \ ) to link ship speed and shaft RPM
• How can you express 12.6 knots in feet per minute so it can be compared with propeller pitch in feet per revolution? • Once you know how many feet per minute the vessel must travel and how many feet per revolution the propeller advances, how can you combine those to find revolutions per minute? • After you compute the RPM, which of the answer choices is closest to your calculated value?
• Convert knots to feet per minute carefully (1 knot = 6080 feet per hour or about 6076 feet per hour depending on the exam standard—verify which value your materials use). • Be sure distance units match: both ship speed and propeller pitch must be in compatible units (feet vs feet) before you divide. • After finding RPM, double-check the arithmetic to ensure it falls in the same order of magnitude as the options (around 80–100 RPM).
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