Question

Find the efficiency of a machine that does 800 J of work if the input work is 2,000 J.

Answer 1

Answer:

Efficiency: 0.4 (40%)

Explanation:

The efficiency of a simple machine is given by the ratio

$\eta = \frac{W_{out}}{W_{in}}$

where

$W_{in}$ is the input work of the machine

$W_{out}$ is the output work of the machine

For the machine in this problem, we have:

$W_{out}=800 J$ is the output work

$W_{in}=2000 J$ is the input work

Therefore, the efficiency of the machine is

$\eta=\frac{800}{2000}=0.4$

Which can be also written as percentage:

$\eta=0.4\cdot 100 = 40\%$