Date post: | 22-Dec-2015 |
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Pulleys and Pulley Systems: Student Learning GoalThe student will be able to construct a system of
pulleys and determine its ideal and actual mechanical advantage (C2.7).
The Pulley
The pulley is a member of the lever family because it is a rigid object that can rotate freely around a fulcrum.
The wheel has a grooved rim in which a rope or cable can run.
A Single Fixed Pulley
A single fixed pulley (in which the fulcrum does not move) gives no mechanical advantage but changes the direction of the effort force (FE) required to lift the load force (FL).
A Single Movable Pulley
A pulley in which the fulcrum does move when the load is moved is called a moveable pulley.
There is a mechanical advantage to using this pulley.
Pulley Systems
A system of pulleys can also give you a mechanical advantage.
The IMA will be equal to the number of support strands (i.e. strands pulling upward). This system of one
fixed pulley and one moveable pulley has 2 support strands.
Pulley Systems: Example
What is the IMA of the pulley system at right?
IMA = 3So you would expect the FE
to be three times less than the FL . . .
Pulley Systems: Example
What is the IMA of the pulley system at right?
IMA = 3So you would expect the FE
to be three times less than the FL . . .
But friction, the mass of the pulleys, etc. will increase your required FE .