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Equilibrium – Numerical Problem

SOLID HEMISPHERE OF RADII R EACH, are placed in contact with each other with each other with their flat faces on a rough horizontal surface. A sphere of mass m and radius R is placed symmetrically on top of them. The normal reaction between the top sphere and any hemisphere assuming the system to be in state equilibrium is

Gravity, Balance and some doubts

Nassar posted: “I have no explanation why did the scale get balanced when there are twe equal masses on both sides ???
Here is the problem:

Suppose that a have a scale and I put 1kg on one side , so this side will get down – no problem with that-


if I put another 1kg but on the other side of the scale…now imagine this,
the first 1kg was down and at this very moment ( I mean before the scales started to get balanced) the new 1kg will be at top , now according to the law of Gravity , the gravitaional force affecting the lower mass is greater than that affecting the top mass (I mean the mass at the bottom is closer to the center of the earth)…
Here is my question:
What force make the mass at the buttom to rise up against the gravity???
All explanations said that its in order to equalaze the gravitational force on both sides , but this makes no sense,

First why to equalize? ,

and second ,

What force make the mass at the bottom to rise ?

For me it is not silly question..
Thank you

This is the type of doubt which we expect from students and visitors. The doubts which we encounter when we think on what we learn.


First of all let us talk about the force of gravity and its (more…)

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