Physics has been useful for human beings since Antiquity, its principles are used to produce objects that make up several tools and utensils that facilitate the most varied tasks, among these objects is the pulley.
Pulleys are also known as pulleys, which are wheels with a central axis and which have a kind of groove through which a rope passes. Sheaves can change the force needed to move heavy objects, both towards and intensity, they can be fixed or mobile, the system with a fixed pulley will only change the direction of force applied. See the image:
Fixed pulley: in this case the pulley only changes the direction of force
However, when you add mobile pulleys to the system, the force needed to perform tasks such as lifting or moving heavy objects, becomes smaller and decreases more and more as we increase the number of pulleys. This system, consisting of one or more mobile pulleys, and a fixed one, is called an exponential pulley and its physical principle is relatively simple, see the diagram:
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System consisting of a fixed and a mobile pulley
By Newton's second law, we have that in the equilibrium T + T = P
Hence 2T = P, then T = P
2
Each mobile pulley cuts the weight in half.
If we have to lift an object of weight "'P" and initially apply a tension force "T" on the rope in a system that has "n" movable pulleys, we have the following situation:
With 1 mobile pulley (n=1)
T = P
2
With 2 mobile pulleys (n=2)
T = P = P
4 22
With 3 mobile pulleys (n = 3)
T = P = P
8 23
We can observe that the exponent of the denominator 2 is equal to the number of pulleys n in each situation. Generally speaking, we have:
An equation to calculate the force “T” for any number of moving pulleys (n).
T = P
2no
By Paulo Silva
Graduated in Physics
Would you like to reference this text in a school or academic work? Look:
SILVA, Paulo Soares da. "Exponential Size"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/talha-exponencial.htm. Accessed on June 27, 2021.
