A block moving horizontally on a smooth surface with a speed of 40 ms^-1 splits into two equal parts. If one of the parts moves at 60 ms^-1 in the…

A block moving horizontally on a smooth surface with a speed of $\displaystyle 40 \mathrm{~ms}^{-1}$ splits into two equal parts. If one of the parts moves at $\displaystyle 60 \mathrm{~ms}^{-1}$ in the same direction, then the fractional change in the kinetic energy will be $\displaystyle x: 4$ where $\displaystyle x=$ \_\_\_\_.