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PULLEYS AND LIFTING - 1

V. Ryan © 2004 - 2012

 

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Pulley systems can be used to lift weights safely and effectively. The diagram below shows a pulley attached to a beam. The rope is ‘pulled’ on the effort side and the weight being lifted is on the right hand side, called the ‘load’.
In general a single pulley is useful as it allows the labourer (shown right) to lift the weight without bending his back. This means it is much safer to lift the weight.

   

   

The diagrams below show how a pulley can be compared to a lever. First draw a fulcrum in the centre of the pulley wheel. Then draw a beam across the centre, balancing on the fulcrum. The comparison with a lever can now be seen clearly. Pulleys are a type of lever.

 
 

MECHANICAL ADVANTAGE

   

Mechanical advantage is defined as the ratio of load to effort. Pulley systems rely on this important relationship between load and effort.

Pulleys like levers rely on mechanical advantage. The higher the mechanical advantage, the easier it is to lift a weight. In the example the LOAD and the EFFORT is equal and consequently there is no mechanical advantage with this single pulley.

   

 
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