Monday, June 25, 2012

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Pulley and their types

Pulley
Pulley is  circular disc having groove in  its circumference. There are three types of  pulley. They are:-
Fixed Pulley:- The type of pulley which donot move up and down with the load is called fixed pulley.




It doesnot magnify the applied force but it changes the direction of force
Work is done againist the gravity without the magnification of effort due to work is not very easy.
VR is 1 because the load will be lifted by the same distance just as the effort moves.


Movable pulley:- The type of pulley which moves up and down along with the load is called movable pulley.


In movable pulley ED  is double than that of LD as the pulley is supported by two ropes and its VR is always 2. The pulley moves up and down whereas th load doesnot move up and down in the application of effort.



Block and tackle:- It is the combined pulley with contain both movable and fixed pulley.  






It helps us in both ways viz (they are):-magnifying the applied effort and changing the direction of force applied.
It VR is found by counting number of pulley. For eg:- velocity ratio of pulley having 4 pulley is 4.














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