5 blocks suspended from ceiling -- What are the tensions?

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Homework Help Overview

The discussion revolves around a problem involving five blocks suspended from a ceiling, connected by strings of negligible mass. The participants are examining the tensions in the strings based on the weights of the blocks, which vary in mass.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the net forces acting on the system, questioning the application of gravitational force in an extended-mass system versus a point-mass system. There are discussions about the upward and downward forces acting on the system as a whole.

Discussion Status

The conversation includes attempts to clarify the forces involved and whether the calculated tension values are accurate. Some participants express uncertainty about the assumptions made regarding the system's configuration and the forces acting on it.

Contextual Notes

There is mention of a diagram uploaded by one participant to illustrate the problem, but its clarity has been questioned, indicating potential communication challenges in understanding the setup.

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Homework Statement



5 blocks connected by strings of negligible masses are suspended from a ceiling by a string of negligible mass. The strings and masses in order from bottom to top are M1, S1, M2, S2, M3, S3, M4, S4, M5, S5

M1 = 2kg
M2 = 1kg
M3 = 1kg
M4 = 2kg
M5 = 10kg

What are the tensions on S1, S2, S3, S4 and S5?

Homework Equations



F=ma

The Attempt at a Solution



Net Force is 0 because the system isn't accelerating.

T_1 = (m_1)a = 2kg(g) = 19.6N
T_2 = (m_1)a + (m_2)a = 2kg+1kg(g) = 29.4N
T_3 = (m_1)a + (m_2)a + (m_3)a = 2kg+1kg(g) + 1kg(g) = 39.2N
T_4 = (m_1)a + (m_2)a + (m_3)a + (m_4)a = 2kg + 1kg(g) + 1kg(g) + 2kg(g) = 58.8N
T_5 = (m_1)a + (m_2)a + (m_3)a + (m_4)a + (m_5)a = 2kg + 1kg(g) + 1kg(g) + 2kg(g) + 10kg(g) = 156N


Supposing this is correct, if we treat all the blocks as one system, the force vector upward from M_5 pointing toward the ceiling and the force vector downward from M_1 pointing toward the ground would both be 156N, yes?
 
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Ocata said:
Supposing this is correct, if we treat all the blocks as one system, the force vector upward from M_5 pointing toward the ceiling and the force vector downward from M_1 pointing toward the ground would both be 156N, yes?
Well, in an extended-mass system (as opposed to a point-mass system), where does the force vector of gravity act?
 
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Ocata said:
...

Supposing this is correct, if we treat all the blocks as one system, the force vector upward from M_5 pointing toward the ceiling and the force vector downward from M_1 pointing toward the ground would both be 156N, yes?
You have a system hanging from the ceiling. There is no M1 or M5 .

The ceiling exerts a force upward on the system. The system exerts a force downward on the ceiling .
 
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SammyS said:
You have a system hanging from the ceiling. There is no M1 or M5 .

The ceiling exerts a force upward on the system. The system exerts a force downward on the ceiling .
Oh, I think I see. Considering the system as a whole, the force of 156N points downwards from the bottom of the system and the force of 156N upwards is from the force of the ceiling on the top string, yes?

By the way, I am guessing the values for the individual tension are correct?
 
Additionally, I am interested is specifying the tension values and uploaded a diagram of this problem and would like to know if the tension values (T) at each connection point is correct.
 

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  • Tension c.JPG
    Tension c.JPG
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Ocata said:
Additionally, I am interested is specifying the tension values and uploaded a diagram of this problem and would like to know if the tension values (T) at each connection point is correct.
Yes, your tension values are correct.

The image is virtually impossible to read. -- very "washed-out" appearance.
 
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Thank you SammyS,

I'll definitely make the contrast darker when I scan next time, thanks.

Regards
 

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