What Is the Weight Attached in a Pulley Traction System in Equilibrium?

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SUMMARY

The discussion focuses on calculating the weight attached in a pulley traction system in equilibrium, where the sum of downward forces at points A and B equals 41 lbs. The tension (T) in the system is constant and equal to the weight (W). The correct calculation yields W = 31.0 lbs, derived from the equation ƩF_y = 0, which incorporates the angles of tension at 25 and 60 degrees. Additionally, the horizontal forces must account for friction between the patient and the bed to achieve balance.

PREREQUISITES
  • Understanding of basic physics principles, particularly forces and equilibrium
  • Knowledge of trigonometric functions, specifically sine
  • Familiarity with tension in pulley systems
  • Ability to set up and solve equations involving forces
NEXT STEPS
  • Study the principles of static equilibrium in physics
  • Learn about tension calculations in pulley systems
  • Explore the effects of friction in mechanical systems
  • Review trigonometric identities and their applications in force resolution
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This discussion is beneficial for physics students, mechanical engineers, and anyone involved in the design or analysis of pulley systems and traction mechanisms.

Missnomer
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Homework Statement


Sum of downward forces exerted at A and B is 41lbs by the leg, what is the weight attached?
Kpvcb5E.jpg


Homework Equations


None, really...


The Attempt at a Solution


Tension (T) throughout the system must be constant and equal to the weight (W).
I first assumed that the leg was entirely pulled up by B since I thought the force passing A
is going down (wrong since this is in equilibrium) and claimed W = 41sin60, but it's not that simple.

Tension pulls both ways, so there is an upward force at A as well as B.
Since
ƩF_y = 0
Tsin25 + Tsin60 - 41lb = 0
T = W = 41 / (sin25 + sin60) = 31.0lb

But using this value of T in checking horizontal forces, they don't balance out.
What am I missing here, or are my calculations correct and there just is a net horizontal force
on the leg that the leg has to resist?

Thanks in advance :).
 
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Missnomer said:

Homework Statement


Sum of downward forces exerted at A and B is 41lbs by the leg, what is the weight attached?
Kpvcb5E.jpg


Homework Equations


None, really...


The Attempt at a Solution


Tension (T) throughout the system must be constant and equal to the weight (W).
I first assumed that the leg was entirely pulled up by B since I thought the force passing A
is going down (wrong since this is in equilibrium) and claimed W = 41sin60, but it's not that simple.

Tension pulls both ways, so there is an upward force at A as well as B.
Since
ƩF_y = 0
Tsin25 + Tsin60 - 41lb = 0
T = W = 41 / (sin25 + sin60) = 31.0lb

But using this value of T in checking horizontal forces, they don't balance out.
What am I missing here, or are my calculations correct and there just is a net horizontal force
on the leg that the leg has to resist?

Thanks in advance :).
The horizontal forces balance if you take into account the friction between the patient and the bed.

AM
 

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