How Does a Pulley Find Its Equilibrium Position in a Static System?

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SUMMARY

The discussion centers on determining the equilibrium position of a pulley system involving a mass suspended by a string fixed at two points, A and B. The key variables include the horizontal displacement w, vertical displacement h, and the length L of the string. Participants emphasize the necessity of applying Newton's first law to establish equilibrium equations and suggest utilizing trigonometric functions to derive the angles Theta(1) and Theta(2), as well as the distances x, y, L1, and L2 at equilibrium. The minimum potential energy principle is also highlighted as a crucial factor in solving the problem.

PREREQUISITES
  • Understanding of Newton's first law of motion
  • Basic principles of potential energy
  • Trigonometry for angle and distance calculations
  • Ability to draw and interpret free body diagrams
NEXT STEPS
  • Study the application of Newton's first law in static equilibrium problems
  • Learn about potential energy minimization in mechanical systems
  • Practice trigonometric calculations related to angles and distances in pulley systems
  • Explore free body diagram techniques for analyzing forces in static systems
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Students in physics or engineering disciplines, educators teaching mechanics, and anyone interested in understanding the dynamics of pulley systems and static equilibrium analysis.

benf.stokes
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Homework Statement



Consider the situation of the figure, where a string of negligible mass and length L is fixed at two points A and B, with B dislocated of A by a distance w(<L) and vertically dislocated by a distance h < sqrt(L^2-w^2) A mass is hung on the rope using a moving pulley of negligible mass. The pulley has no friction and can move freely along the rope until it "finds" the position of equilibrium in which the pulley is at a horizontal distance x of point A, and a vertical distance y of that point.

static_hanging.jpg


What are the equilibrium angles Theta(1) and Theta(2)?
What are the values of x, y , L1 and L2 at equilibrium?

Homework Equations



There aren't any besides the fact that the potential energy must be a minimum

The Attempt at a Solution



I can't even get started.
 
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I haven't looked at this problem in any detail, but it seems that there are enough equilibrium equations, and given geometry, to solve it. You should probably start by drawing a free body diagram of the hanging mass, and writing the 2 equilibrium equations using Newton's 1st law. Note that ideal pulleys change the direction of the tension in the cable, but not its magnitude. Then you've got to do some trig work.
 
Thanks for the reply, but my problems is in the trig work. I don't know how to get started
 

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