Wednesday, February 13, 2008
MECHANISMS:
Levers-are the most simplest of mechanisms. Its discovery dates back to the time of the Stone Age. Heavy loads were then abled to be lifted with a small force using this simple machine.
A lever is basically a beam that rotates around a fulcrum. There will be an effort at one end and the load on the other. As the fulcrum gets closer to the load, the larger the load can also be lifted with the same strength. This is known as a mechanical advantage.
Pulleys- are used to transfer rotating motion through a belt, from one shaft to the other. An example, is that of the vacuum cleaner that transmits the power from the motor to the rotating brushes by pulleys. One point about the pulley is that it always moves at the same speed when their diameter is the same. If one is bigger, then the velocity ratio and mechanical advantage is introduced.
Gears- are basically wheels with teeth. The teeth of a cog mesh with those of an adjoining one and thus transmit rotary motion between the two cogs. Gears always rotate in opposite directions. The speed of the gear depends on the number of teeth one has. For example, when a gear with more teeth meshes with one with less teeth, the gear with the lesser number of teeth will move faster.
