If the speed necessary for reaching port at...

Question 1 of 2707066636eea28f7522a1c51b5b3

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?

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Question 1 of 27070

🔍 Key Concepts

• Propeller slip: relationship between apparent (theoretical) speed from pitch and actual speed of advance • Conversion between knots, feet, and minutes (1 nautical mile = 6076 feet; 1 knot = 1 nautical mile per hour) • Basic speed formula: Speed = Distance / Time and rearranging to find RPM

💭 Think About

• First, convert the vessel’s speed in knots to feet per minute so that its units match the propeller pitch in feet per revolution. • Figure out how many feet of advance you get per revolution when there is a 3% positive slip. How does slip change the effective distance advanced compared to the pitch? • Once you know feet per minute (from speed) and feet per revolution (from pitch and slip), how do you combine them to get revolutions per minute?

✅ Before You Answer

• Be sure to convert knots to feet per minute correctly before doing any RPM calculation. • Apply the 3% positive slip to the right quantity (ask yourself: does positive slip mean the propeller advances more or less than its pitch?). • Before picking an answer, check that your RPM result is close to one of the choices and that the unit is clearly revolutions per minute.