What is the machanical advantage of a machince and explain why the efficency of a machine can't be 100%

The Mechanical Advantage (MA) of a machine is the ratio between the output force produced by the machine divided by the input force exerted on it:

where

is the output force (also called Load)

is the input force (also called Effort)

The MA is generally a number larger than 1, since machines are used to "multiply" the force applied.

There are actually 2 values of the mechanical advantage for a machine:

- The Ideal Mechanical Advantage (IMA), which is the MA when there are no frictional force acting on the machine, and so when all the work done in input is transferred as energy in output

- The Actual Mechanical Advantage (AMA), which is the MA when taking into account the frictional forces, which cause a dissipation of part of the energy; so, not all the work done in input is transferred as energy in output

The efficiency of a machine is defined as the ratio between the two:

A machine cannot have an efficiency of 100% because there are always some frictional/resistive forces acting on the system, so part of the energy in input is always dissipated, and therefore AMA < IMA, and so the efficiency is not 100%.

unlike poles attract