Find the period of small oscillations of a mathematical pendulum of length \(l\) if its point of suspension \(O\) moves relative to the Earth's surface in an arbitrary direction with a constant acceleration \(\mathbf{w}\) (Fig. 4.7). Calculate that period if \(l=21 \mathrm{~cm}, w=g / 2,\) and the angle between the vectors \(w\) and \(g\) equals \(\beta=120^{\circ}\).