A bead, under the influence of gravity, slides along a frictionless wire whose height is given by the function y(x). Assume that at position (x,y) = (0,0), the wire is vertical and the bead passes this point with a given speed v0 downward. What should the shape of the wire be (that is, what is y as a function of x) so that the vertical speed remains v0 at all times?