A circular field has a radius of \(61 \ m\). Students place two rows of flags along equal chords \(WX\) and \(YZ\) with the measurement of \(120 \ m\), each at the same distance from the centre.
(i) The perpendicular distance from the centre \(O\) to each chord is __________ \(m\).
(ii) If another group places a chord \(PQ\) at a distance of \(60 \ m\) from the centre, its length is _________ \(m\).
(iii) Two equal chords in a circle are at distances of \(4 \ m\) and \(9 \ m\) from the centre. Is this construction possible?
(iv) State the general relation between chord length and distance from the centre.