<p>A circular disc reaches from top to bottom of an inclined plane of length l. When it slips down the plane, if takes&nbsp;&nbsp;. When it rolls down the plane then it takes t s. When it rolls down the plane then it takes&nbsp;<span class="equation">\((\frac{\alpha}{2})^{1/2}\)</span>t s, where <span class="equation">\(\alpha\)</span>&nbsp;is_____​​​​​​​​​​​​​​</p>