<p>A uniform rod AB of mass&nbsp; 2 kg and length 30cm&nbsp; at rest on a smooth horizontal surface. An impulse of force&nbsp; 0.2Ns is applied to end B. The time taken by the rod to turn through at right angles will be&nbsp;<span class="equation">\(\frac{\pi}{x}\)</span>&nbsp;S, where x =&nbsp; _______ .</p>