Let us consider a spherical particle of radius a, moving inside a viscous fluid in the low Reynolds number regime. After solving the Stokes equations in Fourier space, for a time dependent point force Fz, acting perpendicularly on the particle, I came out with the attached equation. Here q is the Fourier transform variable and z0 is the vertical position of the point force. How the well-known bulk mobility can be obtained from this equation?
Dear Abdallah
I think Your equation contradicts the second law of Newton. Newton's law says that the acceleration, but not speed proportional to the force.
Я думаю, что Ваше уравнение противоречит второму закону Ньютона. Закон Ньютона говорит о том, что ускорение, но не скорость пропоциаонано силе.
Левъ
I think that in viscous fluid the velocity can be proportional to the force. It is work against the friction of viscous medium. The 2nd law on Newton works on micro level, for each pairwise interaction, but the global motion does not obey it. So I see no contradiction. See for example this text: http://cnx.org/contents/[email protected]:E1HJQcnG@5/Motion-of-an-Object-in-a-Visco
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