Question

How is the mechanical efficiency of a machine usually expressed?

Answer 1

Answer:

As a percentage

Explanation:

The mechanical efficiency of a machine is the percentage of energy in input to the machine that is converted into useful work.

Mathematically, the efficiency of a machine is given by:

$\eta=\frac{W}{E}\cdot 100$

where:

W is the useful work in output from the machine

E is the energy in input to the machine

For example, a machine with 80% efficiency means that it converts 80% of the input energy into work.

A machine can never be 100% efficient, since part of the input energy is wasted due to the presence of frictional forces.

So, the efficiency of a machine is expressed as a percentage.