Statics problem -- Rectangular plate lying on two inclined surfaces

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Homework Help Overview

The discussion revolves around a statics problem involving a rectangular plate resting on two inclined surfaces. Participants are exploring the forces acting on the plate, particularly the normal forces at points A and B, and their relationship to angles α and β.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the equations relating the normal forces and their components along the x-axis and y-axis. Questions arise about the definition of the line of action of forces and its relevance to torque calculations.

Discussion Status

Some participants have provided insights into the importance of the lines of action of the forces and their intersection point. There is an ongoing exploration of how these concepts relate to the equilibrium of the system, particularly regarding the torques exerted by the forces.

Contextual Notes

Participants are grappling with the definitions and implications of forces acting on a body in equilibrium, as well as the specific geometry of the problem involving angles and points of application.

Mzaa
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Homework Statement


https://www.img.in.th/image/VNaqVa
https://www.img.in.th/image/VNa3k9
upload_2018-5-12_11-36-12.png


upload_2018-5-12_11-36-38.png


This is my home work.

Homework Equations

The Attempt at a Solution


I have a problem with the force at A and B. I don't know how to use NA NB in the term of α and β to use moment calculation. I got that In x-axis NAsin∝=NBsinβ, but in the y-axis it still confuse.
 

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Mzaa said:

Homework Statement


https://www.img.in.th/image/VNaqVa
https://www.img.in.th/image/VNa3k9
This is my home work.

Homework Equations

The Attempt at a Solution


I have a problem with the force at A and B. I don't know how to use NA NB in the term of α and β to use moment calculation. I got that In x-axis NAsinα=NBsinβ, but in the y-axis it still confuse.
How many forces act on the plate?
With that many forces acting on a body in equilibrium, what can you say about the lines of action of the forces?
 
I recently searched for definition of "line of action of force",but I still confuse.Are they the line passing through A and B and they're pararelled?
 
Mzaa said:
Are they the line passing through A and B
Yes. The normal force at A passes through point A. This is important for finding the torque that a force exerts about a given axis.
Here you have three forces acting on the plate. The lines of action of the two normal forces intersect at some point, P. If we take moments about that point, what torque do those two forces exert about P?
The third force is gravity.
If the system is in equilibrium, what does that tell you about the torque the gravitational force exerts about P?
 

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