Pulleys

Pulley basics

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Pulley is a device that can increase the magnitude of the effort force. 

Without Pulley

pulley force - no pulley

With no pulley - the effort force is similar to the load - in opposite direction.

S = F (1)

where

S = effort force (N)

F = load (N)

Single Pulley

Fixed Pulley

pulley force - single fixed pulley

With a single fixed pulley the effort force is similar (or more due to efficiency) to the load.

S = F (2)

The advantage with the single fixed pulley is that the direction of force is changed - it is possible to pull down instead of lifting up.

Movable Pulley

pulley force - single movable pulley

 

With a single moveable pulley the effort force is half (or more due to efficiency) of the load.

S = 1/2 F (3)

Combined Pulley

pulley force - combined pulley

With a combined moveable pulley as above - the effort force is half (or more due to efficiency) of the load.

S = 1/2 F (4)

pulley force - combined pulley

With two pulleys and the ropes as above -  the effort force is 1/3 (or more due to efficiency) of the load.

S = 1/3 F (5)

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Related Topics

  • Mechanics Kinematics, forces, vectors, motion, momentum, energy and the dynamics of objects

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  • Lifting Wheels Lifting wheels and effort force

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Resources, Tools and Basic Information  for Engineering and Design of Technical Applications!

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