29/06/2015

SCIENCE FORM 5CHAPTER 5: MOTION /GERAKAN5.7Motion of Vehicles in Water Principle of Operation of Vehicles in Water1) Ship A ship is driven by an engine which turns the propellers. The turning propellers push the water behind (action) and cause a forward momentum (reaction) which drives the ship forward. The rudder of the ship controls the direction of motion of the ship.

2)Hovercraft

- A hovercraft moves on a cushion of air on the surface of the sea.- The engine turns the fans which produce the cushion of air to loft the hovercraft from the sea.- The large fans on top of the hovercraft produce a strong backward wind (action) which causes an equally strong forward momentum in (reaction) that pushes the boat forward.

3)Hydrofoil

The lower surface of a hydrofoil has wing-shaped structures called hydrofoils. At a certain speed, the hydrofoils get lifted above the water surface (aerofoil principle) and the boat moves faster because of reduced friction with the water.

Archimedes Principle

5.8Motion of Vehicles in the Air Principle of Operation of Vehicles in Water1) The Jet engine

- Air is sucked from the front of the engine into the compressor and compressed so that it contains more oxygen for its volume.- The hot compressed air is directed into the combustion chamber where a fuel such as kerosene is sprayed into it.- The mixture of hot air and fuel burns and release hot exhaust gases, which escape from the back of the engine and produce a great backward momentum (action).-This action causes as equally large forward momentum (reaction) which pushes the jet plane forward.

2)The Rocket Engine

- Liquid hydrogen and liquid oxygen are carried in the rocket engine.- The hydrogen fuel burns fiercely in the oxygen in the combustion chamber producing exhaust gases.- The exhaust gases escape from the back of the engine with great backward momentum (action).- This action causes an equally powerful forward momentum (reaction) which pushes the rocket upwards.- Unlike a jet plane, a rocket can move outside the Earths atmosphere because it carries its own hydrogen and oxygen.

Differences between the Jet Engine and the Rocket Engine

Jet engineRocket engineDifferences

Structure

Methods of launching

Source of oxygen

Fuel

Fuel Consumption

Size of thrust

Bernoullis Principle

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