<p>A block moving horizontally on a smooth surface with a speed of 40 <span class="equation">\(ms^{-1}\)</span>&nbsp;splits into two equal parts. If one of the parts moves at 60 <span class="equation">\(ms^{-1} \)</span>​​​​​​​in the same direction, then the fractional change in the kinetic energy will be x : 4 where x = ___________.</p>