Answer :
The correct answer to the question is unitless i.e the IMA of a mechanical system has no unit.
EXPLANATION:
The IMA of a mechanical system stands for ideal mechanical advantage. It can be defined as the number of times the input or effort force provided to the mechanical system is multiplied under ideal conditions. The ideal conditions means that the system is free from friction, air resistance etc.
Let us consider [tex]d_{i}[/tex] is the distance over which the input force is applied.
Let [tex]d_{0}[/tex] is the distance over which the output force is applied.
The ideal mechanical advantage of the system is calculated as -
IMA = [tex]\frac{d_{i}} {d_{0}}[/tex].
Both [tex]d_{i}\ and\ d_{0}[/tex] are measured in distance unit.
Hence, IMA is a unitless physical quantity.