Question on torques. quick one.

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Homework Help Overview

The discussion revolves around a torque problem involving two masses, 'm' and 'M', and their relationship in terms of equilibrium and center of mass. Participants are exploring the calculations related to torque and the resulting ratios.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to establish a relationship between the torques of the two masses and derives a ratio, but encounters a discrepancy with the provided solution. Some participants question the interpretation of the ratio and suggest clarifying the relationship between 'M' and 'm'. Another participant introduces a method involving the center of mass to analyze the equilibrium condition.

Discussion Status

The discussion is active, with participants offering different perspectives on the problem. There is acknowledgment of the original poster's method, and an alternative approach has been presented that appears to be well-received. However, there is no explicit consensus on the correct interpretation of the ratios yet.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information available and the methods they can use. The original poster expresses confusion regarding the expected answer compared to their calculations.

RoboNerd
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Homework Statement


Untitled 3.jpg


Homework Equations


ok, I thought that the torque from the mass 'm' would be equal to torque from mass 'M'

The Attempt at a Solution


I wrote down:

m * g * (d/4) = M * g * d

(m/4) = M

m = 4M

Thus, the ratio is 4M : 1 m, which gives answer 1.

However, the solutions say that the answer is 5.

Could anyone please weigh in, and thanks in advance for the help!
 
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I agree with your answer.
 
RoboNerd said:
Thus, the ratio is 4M : 1 m
No, you have shown 4M=1m. Think of M and m as numbers there. What is M/m?
 
ahh 1/4. Right, thanks!
 
I have another method,
For the system to be in equilibrium the centre of mass should lie exactly on the pivot.

Assume the pivot to be at (0,0)
assume M to be at (d,0)
assume m to be at (-d/4 ,0)
Applying the formula of center of mass
x c.o.m. = (m(-d/4) +Md)/(m+M) = 0

Md = md/4
M:m=1:4
 
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Likes   Reactions: CWatters and RoboNerd
That sir is an awesome and time-saving method! Thanks a lot! Everyone thanks!
 

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