Static equilibrium; pulley and inclined plane problem.

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SUMMARY

The forum discussion focuses on solving a static equilibrium problem involving a pulley system and an inclined plane. The key question is determining the weight WB that maintains equilibrium, with the assumption of negligible friction. The user initially calculated the weight at B as 8.72 lb but later corrected their understanding of unit conversions, confirming that the weight of block A is 175 lb, which equals approximately 79.5 N. The discussion highlights the importance of consistent unit usage in physics problems.

PREREQUISITES
  • Understanding of static equilibrium principles, specifically ΣF=0.
  • Familiarity with unit conversions between pounds and Newtons.
  • Knowledge of pulley systems and tension forces.
  • Basic grasp of inclined plane mechanics.
NEXT STEPS
  • Study the principles of static equilibrium in greater detail.
  • Learn about tension in pulley systems and how it affects equilibrium.
  • Research unit conversion methods, particularly between imperial and metric systems.
  • Explore inclined plane problems and their applications in physics.
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in mastering static equilibrium problems involving pulleys and inclined planes.

J-dizzal
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Homework Statement


What weight WB will cause the system to be in equilibrium? Neglect all friction, and state any other assumptions.
20150703_125114_zpskvhgwrb0.jpg

Homework Equations


ΣF=0

The Attempt at a Solution


I can't figure out what I am doing wrong with these pully problems, I tried putting in resultant forces at pully A, but that just added another variable.[/B]
20150703_124617_zpsxzgyk5c7.jpg
 
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You should check the Wb is Tb or ___ ?
 
I did a redo of the tensions this time starting from A going to B, I am still missing something though. solving for weight at B i got 8.72lb (on the right side of my paper)
20150703_131312_zps5z8gcb8z.jpg
 
It seems correct to me.
 
Thyphon said:
It seems correct to me.
Yea, but I am still missing something, its not the correct answer.
 
Oh, find the F again you will see the wrong :) 79,5 N or kg ?
 
Thyphon said:
Oh, find the F again you will see the wrong :) 79,5 N or kg ?
If the weight of block A is 175 lb that is equal to 79.5N
 
ok i got, my mistake was trying to convert from english to standard, i should of just left it in english. thanks thypon.
 
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No, 1lb is equal to 0,453 kg, so 175lb =79,27 kg
N means kg*m/(s^2)
 
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  • #10
Thyphon said:
No, 1lb is equal to 0,453 kg, so 175lb =79,27 kg
N means kg*m/(s^2)
i got confused because 175 lb of weight = 175 lb mass.
 
  • #11
Is it okay now ?
 
  • #12
Thyphon said:
Is it okay now ?
yea its correct now. thanks
 
  • #13
Why is the tension T/2?
 

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