Aside from the fact that speed is implied by velocity (velocity being a vector, while speed is a scalar), you still need to specify whether it’s an African or a European swallow.
Assuming the problem is not ambiguous and a unique solution exists, we are looking for a velocity vector v(r,theta, phi) which is independent of the direction of flight since the swallow can be flying anywhere. The position vector, expressed in spherical coordinates, is v=. In order for the position vector to be independent of the azimuthal and polar angles theta and phi respectively, we must have dv/d(theta)=0 and dv/d(phi)=0 (partial derivatives). This only holds when r=0 - therefore the speed of the swallow is zero and it must be stationary.
^I’ll just define local generalized coordinates q such that it isn’t a problem for the angles to be independent, and then the swallow can be going whatever speed it wants.
