Two hanging masses and three strings

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SUMMARY

The discussion focuses on a physics problem involving two hanging masses, m and M (where M = 2m), connected by three strings in equilibrium. The participant attempts to determine the tension in the strings and the angle theta using the equilibrium condition ΣF = 0. Key insights include that the y-component of the tensions in the diagonal strings supporting mass m must equal mg, and the tension in the third string connecting mass M to a fixed point can be derived using the same equilibrium principles. The participant is encouraged to apply ΣF = 0 to mass M to find the unknowns rather than guessing values.

PREREQUISITES
  • Understanding of Newton's laws of motion, specifically F = ma
  • Knowledge of equilibrium conditions in static systems
  • Familiarity with vector components of forces
  • Basic trigonometry, particularly sine and cosine functions
NEXT STEPS
  • Apply equilibrium equations to solve for tensions in multi-mass systems
  • Learn about vector decomposition of forces in physics
  • Study examples of static equilibrium problems involving multiple strings and angles
  • Explore the concept of tension in strings and its applications in physics
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and static equilibrium, as well as educators seeking examples of tension problems in multi-body systems.

Lennie
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Homework Statement


Two masses m and M (where M = 2m) are attached with strings. One mass m is suspended from a single vertical string held by two strings each at 45 degrees to the horizontal. The suspending string to the left at 45 degrees is attached to a fixed point. The string on the right at 45 degrees is attached to another mass M which in turn is attached by a further to a fixed point above at an angle theta to the horizontal.
If the system is in equilibrium, determine the tension in the three strings in terms of m and g, and calculate the angle theta.[/B]

Homework Equations


F = ma

The Attempt at a Solution


As the system is in equilibrium i can say a=0 and therefore ΣF = 0.
The y component of the two tensions in the two diagonal strings supporting mass m should be equal to mg when summed. Assuming the tensions are still equal (not quite sure what effect the other mass M would have on this - mass M is what has thrown me) then the tension in the bottom two strings should be mg/√2 ?
The tension in the 3rd string connecting mass M with the fixed point ? My best quest was to say it is equal to √2mg as 2mg sin45 = T ?
I also don't know theta however and don't see a way of finding it, at this point I am almost sure i have absolutely none of this right! Any help on a method to solve this would be much appreciated!

P.s sorry for the lack of image, can't seem to find anything on the web which shows a similar situation.
 
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Lennie said:
As the system is in equilibrium i can say a=0 and therefore ΣF = 0.
Good.

Lennie said:
The y component of the two tensions in the two diagonal strings supporting mass m should be equal to mg when summed.
Good.

Lennie said:
Assuming the tensions are still equal
No need to assume that... prove it!

Lennie said:
The tension in the 3rd string connecting mass M with the fixed point ? My best quest was to say it is equal to √2mg as 2mg sin45 = T ?
Why guess? Apply ΣF = 0 to mass M and solve for the unknowns.

Lennie said:
P.s sorry for the lack of image, can't seem to find anything on the web which shows a similar situation.
You can use the whiteboard to slap something together yourself.
 

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