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# How does a ship's propeller work?

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A vessel's propeller works by thrusting a column of water away from the main body of the ship, thereby producing a reactive force that moves the boat forward. Most naval vessels use a screw-type propeller that transmits thrust through the main shaft to the thrust bearing. This reactive force reacts to the backward force of the water column to push the boat forward.

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Credit: Sami Sarkis Photographer's Choice RF Getty Images

Propeller blades rotate downward while water rushes in to fill the space left behind to create a pressure differential. Water accelerates from the front of the propeller towards the back, creating a column of water slightly bigger than the propeller itself. Higher velocity creates a water jet out of the rear of the propeller, which adds momentum and thrust to the water. This thrust moves the boat forward. Propeller blades work in water much like fan blades work in air.

The main thrust bearing is located at the forward end of the main shaft within the gear casing. A reduction gear connects to the main shaft which, in turn, connects to the propeller. Reduction gears reduce high rotational speeds of the engine so the propeller functions at lower rotational velocities. Gears allow the engine and propeller to work efficiently.

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## Related Questions

• A:

The maximum speed of a propeller occurs at its tip, and this speed is equal to the vector resulting from its forward speed and tangential velocity. This speed is the helical velocity at the propeller tip.

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There are different decks of a ship, but the primary deck of the vessel is called the main deck. The main deck may be in different locations, depending on the type of ship. It is not usually the topmost deck.

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As of January 2015, historians and archaeologists do not know when the very first individual ship was built. However, it is known that the ancient Egyptians were able to create watercraft with hulls using wooden planks and sails as early as 3000 BC.