For a machine of a given design, due to friction and weight of the moving parts of machine, the velocity ratio does not change, but both mechanical advantage and the efficiency decreases.
Velocity Ratio : It is the ratio of the velocity of effort to the velocity of load. i.e.,
$\mathit{V}.\mathit{R}=\frac{{\mathit{V}}_{\mathit{E}}}{{\mathit{V}}_{\mathit{L}}}$