Static equilibrium marbles problem

AI Thread Summary
The discussion revolves around a static equilibrium problem involving two stacked marbles in a container. The user seeks to determine the forces exerted at contact points A, B, and C, as well as the forces each marble exerts on one another. Initial calculations for the force at point B are straightforward, as it equals the combined weight of the marbles. However, confusion arises regarding the torque calculations, particularly the choice of pivot point for evaluating moments. The user acknowledges a mistake in neglecting the force from the container at point C affecting the bottom marble.
krko
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Hey all, new member here

Homework Statement


Two uniform 75g marbles 2cm in diameter are stacked on top of each other in a container that is 3cm wide
the top marble touches right side of the container, the bottom touches the left side.
Point A is the bottom marble left contact point with the container, point B is the bottom marble touch the bottom of the container, point c is the top marble's contact point with the container

Attempt at a figure:
l top marble, point Cl
lmarble contact pointl
lpoint A, bottom marble l
l_____point B________l
What is the force the container exerts at point A,B, and C?
What force does each marble exert on each other?

Homework Equations


Basically since its static equilibrium, , all force and torques add up to zero. Also the equation for Torque, T=sin(phi)*lever arm

The Attempt at a Solution



force at B is easy to get since that's just the normal force equal to the combined weight of the two marbles.
At A and C, its obvious that they're equal. I can also get the torque due to the top marble on the bottome marble: weight*(.01m)*(sin(30)) after that I don't know what else to do.
 
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Welcome to PF!

Hey, krko ! Welcome to PF! :smile:
krko said:
… I can also get the torque due to the top marble on the bottome marble: weight*(.01m)*(sin(30)) after that I don't know what else to do.

Is this frictionless?

You're taking moments about the point of contact between the marbles … why? :confused:

If you take moments (torques) about a point, you must do it for all the forces … that's why we usually choose a point about which some of the forces have zero moment.

Try again, taking moments about a different point. :smile:
 
Okay, i uploaded an image of the problem. The torque I'm talking about is the torque caused by the top marble about point the center of the bottom marble. Although looking back i think I found my mistake, that I neglected the effect of the force of the container on point C on the bottom marble.
 

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