9.34 *** at a point p on the earth's surface, an enormous perfectly flat and frictionless platform is built. the platform is exactly horizontal — that is, perpendicular to the local free-fall acceleration g p. find the equation of motion for a puck sliding on the platform and show that it has the same form as (9.61) for the foucault pendulum except that the pendulum's length l is replaced by the earth's radius r. what is the frequency of the puck's oscillations and what is that of its foucault precession? [hints: write the puck's position vector, relative to the earth's center 0 as r r , where r is the position of the point p and r = (x, y, 0) is the puck's position relative to p. the contribution to the centrifugal force involving r can be absorbed into g p and the contribution involving r is negligible. the restoring force comes from the variation of g as the puck moves.] to check the validity of your approximations, compare the approximate size of the gravitational restoring force, the coriolis force, and the neglected term m (st x r) x st in the centrifugal force.