Hi there, I'm trying to comprehend Dirac Delta functions. Here's something to help me understand them; let's say I want to formulate Newton's second law F=MA (for point masses) in DDF form. Is this correct: [tex] F_i = \int [m_i\delta (x-x_i) a_i\delta (x-x_i)]dx[/tex] Or is it this: [tex] F_i = [\int m_i\delta (x-x_i)dx] [\int a_i\delta (x-x_i)dx][/tex] Or is the idea of a Dirac delta function for the instantaneous acceleration of a point mass not well defined? ...or? I intially thought the first equation was correct, but then I worried that infinities were being multiplied, and so, I figured that each delta function would need to be integrated first, before the multiplication takes place, hence the second equation. Any thoughts would be most welcome!