5. A particle of mass \(m \mathrm {~kg}\) is attached to one end of a light inextensible string. The other end of the string is attached to a fixed point \(O\). The particle is set in motion such that it moves in a horizontal circle of radius 2 m with constant speed \(4.8 \mathrm {~ms} ^ { - 1 }\). Calculate the angle the string makes with the vertical.