Equilibrium
Here is shown an easy structure in which the angle in A may varies. For which value of
α
the structure is not stable?
N.B. the angles are positive if anti-clockwise, so for example the angle shown in the pic is positive
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1 solution
In classical mechanics for one rigid body we need 2 fixed centers in order to avoid every movement. In the picture the costrain in B is a fixed center (no displacement in horizontal and vertical directions) while in A the costrain gives us no displacement in the direction orthogonal to the sliding axis, so the center will be placed somewhere on this direction. When this direction will pass through the costrain B, then we will have just one fixed center, so the structure will be not stable. The angle for which this happens is equal to -arctan(L/H).