Weight distribution of 2 configurations

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Discussion Overview

The discussion revolves around the weight distribution of an object (Object-A) in two configurations represented by diagrams (Figure-1 and Figure-2). Participants explore the implications of weight distribution along the bottom edge of a rectangle (Rectangle-B) and the conditions under which this distribution may vary. The conversation includes elements of physics concepts such as Free Body Diagrams (FBDs) and moments, with a focus on understanding the underlying mechanics rather than providing definitive answers.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that the weight distribution in Figure-1 is even along the bottom edge of Rectangle-B.
  • Others challenge this view, stating that the force distribution is not uniform and is higher toward the center than the edges.
  • A participant suggests that the moments around the center of mass must balance in both configurations.
  • There is a discussion about the relevance of Free Body Diagrams (FBDs) and the summation of forces and moments in analyzing the problem.
  • One participant expresses frustration at not receiving direct answers and indicates a desire for a more straightforward explanation rather than guidance towards self-discovery.
  • Another participant encourages the use of online resources to understand the concepts better.
  • A later reply requests intuitive insights about the problem, indicating a desire for personal interpretations rather than technical calculations.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the weight distribution in the two configurations. There are competing views regarding the uniformity of the force distribution along the bottom edge of Rectangle-B, and the discussion remains unresolved with varying interpretations of the physics involved.

Contextual Notes

Some participants reference the need for calculus to understand force distribution, indicating that the discussion may depend on varying levels of mathematical background and familiarity with physics concepts.

Who May Find This Useful

This discussion may be of interest to individuals exploring concepts of weight distribution, mechanics, and the application of Free Body Diagrams in physics, particularly those looking for a deeper understanding of the subject matter without seeking definitive answers.

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TV Weight distribution 02b 500h.jpg


Say Object-A weighs 100 lbs.
In Figure-1, it's obvious that the weight distribution is even along the bottom edge of Rectangle-B.

In Figure-2, ignoring the weight of the white objects, is the weight distribution exactly the same along the bottom edge of Rectangle-B as it is in Figure-1?
 
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What do you think, and why? Are you familiar with how to draw Free Body Diagrams (FBDs) and sum forces and moments?
 
HRG said:
Summary:: Weight distribution

View attachment 253509

Say Object-A weighs 100 lbs.
In Figure-1, it's obvious that the weight distribution is even along the bottom edge of Rectangle-B.

In Figure-2, ignoring the weight of the white objects, is the weight distribution exactly the same along the bottom edge of Rectangle-B as it is in Figure-1?
Hint: The moments around the center of mass must balance in both cases.
 
berkeman said:
What do you think, and why? Are you familiar with how to draw Free Body Diagrams (FBDs) and sum forces and moments?
Nope. I'm just a curious senior. This is not a homework problem.
 
A.T. said:
Hint: The moments around the center of mass must balance in both cases.
You totally lost me. I'm just a curious senior hoping for an explanation from the gurus.
 
HRG said:
You totally lost me. I'm just a curious senior hoping for an explanation from the gurus.
It's good to be curious. Google "sum of moments" and "free body diagram".

Senior in high school? :smile:
 
berkeman said:
It's good to be curious. Google "sum of moments" and "free body diagram".

Senior in high school? :smile:
Nope, senior as in 79 years old.
 
HRG said:
Nope, senior as in 79 years old.
Ah, got it, LOL.

What is your math background? It doesn't take advanced math to work out a sum of moments (a moment is basically a torque, multiplying the force by the lever arm length, and ratioed to the angle that the force is applied at the end of the lever arm).

Here is a basic article about FBDs:

https://en.wikipedia.org/wiki/Free_body_diagram

And here are the Google search results for Sum of Moments:

https://www.google.com/search?q=sum...VCMH0KHXDbAcMQ_AUIDCgA&biw=1206&bih=564&dpr=1

which includes a couple instruction videos on how to apply the sum of moments to solve a statics problem like the one you have asked about. :smile:
 
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HRG said:
Summary:: Weight distribution

View attachment 253509

Say Object-A weighs 100 lbs.
In Figure-1, it's obvious that the weight distribution is even along the bottom edge of Rectangle-B.
This is not correct. The force distribution along the bottom edge of rectangle B in Figure 1 is not uniform. It is higher toward the center than towards the edges.

Have you ever had a course in calculus? If you are talking about the force distribution along the bottom edge, are you comfortable with the idea that the force distribution is described by the local value of the upward force per unit width?
 
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  • #10
Chestermiller said:
This is not correct. The force distribution along the bottom edge of rectangle B in Figure 1 is not uniform. It is higher toward the center than towards the edges.

Have you ever had a course in calculus? If you are talking about the force distribution along the bottom edge, are you comfortable with the idea that the force distribution is described by the local value of the upward force per unit width?
Let me reword my statement.

"In Figure-1, if 2 small blocks of wood are placed underneath Rectangle-B, one flush with the left edge and the other flush with the right edge, then the weight pressing on each block would be identical assuming the load is directly in the center of Rectangle-B."

Will the same condition exist in Figure-2?
 
  • #11
HRG said:
Will the same condition exist in Figure-2?
What do you think and why? (Have you actuially been reading the links and hints we have been giving you? )
 
  • #12
Yes, I googled the suggestions but could not figure out the answer to my question. That's OK. I didn't come here for a physics lesson. I should have known better having read replies to questions from other people. I just hoped for an answer but it's like pulling teeth.

I understand that gurus here don't want to give answers. Only to guide people to figuring out the answers for themselves. No problem with that. It's just not my goal at 79 years.

Bye physicsforum. There's no point in my returning.
 
  • #13
HRG said:
I understand that gurus here don't want to give answers. Only to guide people to figuring out the answers for themselves. No problem with that. It's just not my goal at 79 years.
Thanks for the complement. That is indeed what we try to do. Best wishes.
 
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  • #14
BTW, I think I asked a couple times what you think about the problem, but I don't think you replied to that. I know what I think intuitively and with just basic visualization of what would happen, but I'd need to do the FBDs and calculations to be sure.

Can you say what you feel intuitively would happen (before you leave us)? Thanks.
 

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