A solid sphere of mass $2 \mathrm{~kg}$ and radius $1 \mathrm{~m}$ is free to rotate about an axis passing through its centre. A constant tangential force ' $\mathrm{F}$ ' is required to rotate the sphere with $10 \mathrm{rad} \mathrm{s}^{-1}$ in $2 \mathrm{~s}$ starting from rest. Then the value of $\mathrm{F}$ is ____