Maximizing Efficiency: Solving Problems with Ease

[robotman]

Homework Statement

Efficiency is defined as work-out/work-in. Muscles operate with an efficiency of about 18.50 percent in converting energy internally into work externally. Accordingly, how much energy will be expended by a 56.40 kg person in the process of ascending several flights of stairs to a height of 20.60 m?

Relevant Equations

mgh

How to use efficiency in this problem?

 

[haruspex]

Homework Statement:: Efficiency is defined as work-out/work-in. Muscles operate with an efficiency of about 18.50 percent in converting energy internally into work externally. Accordingly, how much energy will be expended by a 56.40 kg person in the process of ascending several flights of stairs to a height of 20.60 m?
Relevant Equations:: mgh

How to use efficiency in this problem?

How much mechanical work has to be done to raise a mass m by height h?

 

[BvU]

Hello again,

$mgh$ is not a cure-all , but here $$ \text {work } = mgh $$ is indeed useful !

How to use efficiency in this problem?

use $$\text {efficiency} \equiv {\text {work out}\over\text {work in}} $$