Torque around a point from lever linkage

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Homework Help Overview

The discussion revolves around a torque problem involving a lever system with multiple linkages. The original poster describes a scenario where a force acts at one end of a lever, and they are trying to resolve the torque around a fixed point in the system. The problem involves understanding the interactions of forces through the linkage and calculating the resulting torque.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss drawing force vectors on a diagram to visualize the problem. The original poster attempts to equate forces through the lever and questions the interaction of forces along the linkage. There are inquiries about equilibrium equations at specific points in the system.

Discussion Status

Participants are actively engaging with the problem, offering suggestions for visualizing forces and discussing equilibrium conditions. There is an ongoing exploration of how to determine the force at a specific point and its implications for torque calculations. No consensus has been reached regarding the correct approach or assumptions.

Contextual Notes

The original poster has indicated they have all necessary lengths and angles but are unsure about the force interactions within the linkage. There is a focus on understanding the dynamics of the system rather than arriving at a final solution.

BatsDude
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Hi all. Brushing up on some of my force and torque stuff so I can do some modelling in software.

Homework Statement


I have a system as shown in the picture. A force F acts at point A, which is the end point of the lever AB. Connected to the lever is a link BC, and connected to BC at point C is another link CD, which is anchored to the ground.
I'm trying to resolve this into a torque around the point D. I know the lengths, and all the angles involved, I'm just confused about how the force travels through the linkage.
SWs7w.png


Homework Equations


T = F*r*sin(theta) is the equation for torque from a force acting at an angle

The Attempt at a Solution


My attempt was to try and equate the forces through the lever first.
Let F_b be the output force of the lever at point B, resulting from F acting at point A.
F*(alpha/2)*sin(theta) = F_b*(alpha/2) *sin(phi). Solve for F_b.
From here, I would assume that this force F_b is acting on member CD at an angle of omega and at a lever length of lambda. From this I can calculate the torque around D.

However, I'm not at all sure if this is correct.
 
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Draw the vectors representing the forces directly on the diagram . You should be able to see a way of solving this and similar problems very easily .

Just for interest - since you mention software modelling - you can use a modern cad system as a visual calculator for linkage problems .
 
Hi Nidum,
Thanks for your reply. I've drawn the force vectors that I think are happening, as seen below. Is that correct? The main issue I'm having is actually determining the value of F_b and whether or not it interacts along BC or if it acts at an angle on BC.
fjgS2Px.png
 
Anyone able to help?
 
BatsDude said:
determining the value of F_b and whether or not it interacts along BC or if it acts at an angle on BC.
Let the tension in BC be T (your Fb).
What equilibrium equations can you write for the point B?
What equilibrium equations can you write for the point C?
 
So would the torque around D just boil down to = F_b*lambda*sin(omega)?

Where F_b is = [ F*(alpha/2)*sin(theta) ] / [ (alpha/2)*sin(phi) ]
 
BatsDude said:
So would the torque around D just boil down to = F_b*lambda*sin(omega)?

Where F_b is = [ F*(alpha/2)*sin(theta) ] / [ (alpha/2)*sin(phi) ]
Yes.
 
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Thank you for your help!
 

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