Solutions:

A perfect machine is one whose parts are weightless and frictionless, with no energy dissipation occurs in any way. Because the work output equals the work input, the efficiency is 100 percent.

Ideal Machine :

(a) 100 percent efficiency
(b) Parts are weightless, elastic, and completely smooth.
(c) No loss in energy due to friction

(d) Work input and output are always equal.

Practical machine :

(a) The efficiency of the machine is less than 100%

(b) Parts are not weightless, elastic, or flawlessly smooth 
(c) Friction always causes some energy loss 
(d) Work output is always less than work input