The universal equation of all the beams are given by the famous equation E I V 4 prime being plus rho S V dot dot being 0. That the basic universal equation of dynamics of beams. Well, that's the first miracle that this equation holds, the bending behavior of any beam. But the second miracle is that in general case it has a generic solution that we can now explicitate. The only condition is that the beam is prismatic, which means that the cross section and the material is constant along X. That's the general case for technological reasons because the beam is made by extrusion, which means that the cross section is constant. So any industrial beam is a prismatic one, which means that this coefficient and this coefficient are constant. In this frame, we can propose a classical solution, which is the Lagrange solution of beams considering that the x and t variables are independent one of the other. That's the classical hypothesis of classical physics, which means that V of x, t is the product of a certain function of x multiplied by a certain function of t. Now, let's inject this solution in the dynamic equation. And that's very simple because any scientific progress is simple and it's a huge progress. You will see now that this gives E I F 4 prime g plus rho S F g dot dot, sorry, g dot dot being 0. Then this gives something very simple, which is g dot dot on g being minus E I F 4 prime on rho S F. And you'll see that we are authorized to do this to divide by g and f because if g or f was 0, it should be statics. Which is not interesting because we are trying to find the dynamic solutions. So, let's consider these two functions. This one is depending on the on time and this function is depending only on x. And we suppose that these two parameters are independent, one of the other. Then this one is valid for any time, any time. Well we have the eternity somewhere. And this one is valid for any x on the beam. So we need to have x between 0 and L. So there is a very simple theorem saying that when two functions, continuous functions, of two independent variables coincide (This is identical, equality), coincide on two continuous interval of the real body, they are equal to a constant. A constant which is independent from t and x. And that the genius equation, which will allow us to find the generic solution of this equation. Let's get into the generate solution of the universal equation of the dynamics of beams. Which is under the shape of g dot dot on g being equal to minus E I on rho S F 4 prime on F being a constant. As this identity is okay on two continuous intervals. Then let's look, let's contemplate this equation. This is simply the ratio of the second derivate with the function of time, which must be equal to a constant. And in fact, this is the ISAE-SUPAERO basic definition of a linear structure. Which is a dynamic system, whose temporal solution is the canonical function sign, which is cosine, omega t. And the characteristic of this function is to induce the minus Omega square when it is derivate two times and this is exactly what happens. So we can even get further with the definition of this constant, which is simply minus Omega square. Let's look at this, one second. Minus Omega square is Omega is a real number and not only a real number a positive and strictly positive number, due to the sense of the time, the orientation of the time. Then we are sure that this number is a negative one because minus the square of a real is negative of course. So the good new is that we have solved the dynamic problem. Yes. Yes. Because the dynamics is now included in this linear functions. Well, the rest is now in the space function which is F. And a miracle is that we can explicitate this function in the general case. And this explicitation gives simply the algebraic solution of this equation with this, and this. What does it give? It gives F of x being A cosine Omega x plus B sign Omega x plus C hyperbolic cosine, Omega x plus D hyperbolic sign Omega x. And this solution, which is simply the solution of this equation, is the universal space solution of any beam in the universe. Well well, we must see that this big Omega coefficient is not identical to the temporal pulsation. But it's easy to see that through this constant there is a bi-univoque relation between this space coefficient and this temporal pulsation. And this relation is very simple. Omega square on Omega 4, take care it's not the same Omega here and here. Omega square on Omega 4 being simply E I on rho S. And this is by definition, if you add this additional condition with the space and temporal solution, we got the generic universal solution of any dynamic bending beam in the universe. [MUSIC]