Efficiency is adimensional, meaning there is no associated unit, just a number - and the number should be the same in different measurement systems. Efficiency can be any number between 1 (equivalent to 100%) and 0 (equivalent to 0%).
Efficiency is normally written as a percentage, and does not have an SI unit."percent". It has no units.
In SI units, that would be the Newton.In SI units, that would be the Newton.In SI units, that would be the Newton.In SI units, that would be the Newton.
there is no unit. its usually a percent. so it would be something like joules/joules, which would be nothing.
Derived SI units.
SI and metric are the same units.
International System of Units (SI)
Base units
most of the world does SI so more people can understand with it in SI units
most of the world does SI so more people can understand with it in SI units
SI units are more accurate than English system units
The SI has 7 base units. These units can be combined in an almost unlimited way to form other (derived) units. The Wikipedia article on "SI derived units" lists some examples.
Si and metric are the same thing. SI was a redefinition of metric in 1960.