Two circles with centres \(O\) and \(O'\) of radii 24\(cm\) and 7\(cm\) respectivley intersect at points \(P\) and \(Q\) such that \(OP\) and \(O'P\) are tangents to the two circles. Find the length of the common chord \(PQ\).
\(\angle OPO'\) is
Length of \(OO'\) is
Length of \(PQ\) is