How is the mechanical advantage related to the velocity ratio for (i) an ideal machine, (ii) a practical machine?
All practical machines have friction and hence the output energy is always less than the input energy.
Therefore the efficiency of all practical machines is always less than 1.
By some good manufacturing technology and using high quality and suitable lubricants we can make the efficiency nearly equal to 1.
(i) The ideal machine has an efficiency 1.
Efficiency = Mehanical Advantage / Velocity Ratio.
For ideal machine efficiency = 1.
Hence M.A = V. R.
The V. R of an ideal machine and the practical machine is a constant or is the same for both.
(ii) For a practical machine, M. A will be less than V.R.
Hence we can say that the maximum M. A is the V.R.
For example, the V. R of a pulley is 1.
M.A will be less than 1, due to friction.