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  1. TheGreatDeadOne

    Conservation of momentum in an oblique launch and projectile explosion

    I used the center of horizontal momentum frame. I just used the y-moment to find the angle of the velocity component, so I can write the velocity in the horizontal direction. I'll edit the equations to make it clearer
  2. TheGreatDeadOne

    Conservation of momentum in an oblique launch and projectile explosion

    This problem I already solved using another resource (just get the coordinate of the center of mass reach and from it, get to the larger mass. R = (3v02) / (4g)). But I'm having some trouble calculating using moment conservation. Here what I've done so far: $$ 3\vec v_0 = \vec v_1 +2\vec v_2 $$...
  3. TheGreatDeadOne

    Speed of a hanging rope sliding on a nail (using energy conservation)

    "In (1) and (3), what is the initial height of the mass center of each side?" I was trying to calculate from the end of the string, but really from the center of mass it seems a lot simpler. "In (2), you have a factor x (l-x) in the GPE term, but it is (l-x)^2 in (4). Do you see the asymmetry...
  4. TheGreatDeadOne

    Speed of a hanging rope sliding on a nail (using energy conservation)

    You're right! It's as simple as that. But, the logic used to express the initial and final energies do you think is right?
  5. TheGreatDeadOne

    Speed of a hanging rope sliding on a nail (using energy conservation)

    I solved this problem easily using Newton's second law, but I had problems trying to use mechanical energy conservation to solve it. How I solved using Newton's second law: ##\text{(part of the rope that is on the left)}\, m_1=x\rho g,\, \text{(part of the rope that is on the right)}\...
  6. TheGreatDeadOne

    I Using recurrence formula to solve Legendre polynomial integral

    I am trying to prove the following expression below: $$ \int _{0}^{1}p_{l}(x)dx=\frac{p_{l-1}(0)}{l+1} \quad \text{for }l \geq 1 $$ The first thing I did was use the following relation: $$lp_l(x)+p'_{l-1}-xp_l(x)=0$$ Substituting in integral I get: $$\frac{1}{l}\left[ \int_0^1 xp'_l(x)dx...
  7. TheGreatDeadOne

    Using the Divergence Theorem on the surface of a sphere

    Sorry, I forgot to organize and correct something here. 1 / | r-r '| is a scalar, in my papers I was disregarding the module, forget that part of the divergence theorem.
  8. TheGreatDeadOne

    Using the Divergence Theorem on the surface of a sphere

    it's a scalar (lol I saw the error here, i forgot to fix it here)
  9. TheGreatDeadOne

    Gradient of 1/|r-r'|

    Spherical coordinates. Using Cartesian coordinates I solve correctly, i am trying for spherical coordinates.
  10. TheGreatDeadOne

    Using the Divergence Theorem on the surface of a sphere

    The integral that I have to solve is as follows: \oint_{s} \frac{1}{|r-r'|}da', \quad\text{ integrating with respect to r '}, integrating with respect to r' Then I apply the divergence theorem, resulting in: \iiint \limits _{v} \nabla \cdot \frac{1}{|r-r'|}dv' =...
  11. TheGreatDeadOne

    Gradient of 1/|r-r'|

    Doing R=|r-r'|, i get the expected result: \nabla \frac{1}{|r-r'|} = -\frac{1}{R^2}\hat r=-\frac{(r-r')}{|r-r'|^3} But doing it this way seems extremely wrong, as I seem to be disregarding the module. So I tried to do it by the chain rule, and I got: \nabla...
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