HOW A SHIPS MOVES
- Parent Category: Technical Articles
- In: Ship construction and Naval Architecture
- 17Nov2009
- Last Updated on Tuesday, 13 September 2011 17:16
- Published Date
- By sivasankar
- Hits: 932
How a ship moves ahead?
- We all know that a ship is moving with the help of a proulsion device
How a ship moves ahead?
- We all know that a ship is moving with the help of a propulsion device. Now lets consider the case of a simple propeller of fixed pitch.
- Main engine or whatever may be the propulsor, when it rotates it imparts momentum to the medium (ie) to the water.
- When a propeller is rotating, it produces thrust on water. Now the thrust from propeller is transferred to the water. Since the amount of water is enormous according to Newtons Third Law, the thrust comes back to the ship.
- This thrust is acting on the ship as shown in the figure 1 down below.
Why do we need astern movement?
It may seem a bit strange that one asks why an astern movement is required on any means of land transport, but yes this question certainly has a relevance in context of shipping (as well as aviation). A ship normally would not move in the astern direction but here are a few situations wherein the navigation officers might be required to move the ship in astern direction and these situations can be either of the following
- Astern movement is given to stop the ship soon. Even when the engine is stopped, due to the momentum, the ship will further move to some extent.
- At this situation when you give astern movement, this momentum will be stopped as the propeller starts to rotate in other-way-round.
- This is achieved by means of reversing the engine.
- Now lets consider the case of a simple propeller of fixed pitch.
- Main engine or whatever may be the propulsor, when it rotates it imparts momentum to the medium (ie) to the water.
- When a propeller is rotating, it produces thrust on water. Now the thrust from propeller is transferred to the water. Since the amount of water is enormous according to Newtons Third Law, the thrust comes back to the ship.
- This thrust is acting on the ship as shown in the figure 1 down below.
Why do we need astern movement?
It may seem a bit strange that one asks why an astern movement is required on any means of land transport, but yes this question certainly has a relevance in context of shipping (as well as aviation). A ship normally would not move in the astern direction but here are a few situations wherein the navigation officers might be required to move the ship in astern direction and these situations can be either of the following
- Astern movement is given to stop the ship soon. Even when the engine is stopped, due to the momentum, the ship will further move to some extent.
- At this situation when you give astern movement, this momentum will be stopped as the propeller starts to rotate in other-way-round.
- This is achieved by means of reversing the engine.
