Question

1. the average human lung expands by about 0.50 l during each breath. if this expansion occurs against an external pressure of 1.0 atm, how much work (in j) is done during the expansion?

Explanation:

Step1: Recall work - pressure - volume formula

$w=-P\Delta V$

Step2: Convert units

We know that $1\ atm = 101325\ Pa$ and $1\ L=1\ dm^{3}=10^{- 3}\ m^{3}$. So, $\Delta V = 0.50\ L=0.50\times10^{-3}\ m^{3}$ and $P = 1.0\ atm=101325\ Pa$.

Step3: Calculate work

$w=-P\Delta V=-(101325\ Pa)\times(0.50\times 10^{-3}\ m^{3})=- 50.6625\ J\approx - 51\ J$. The negative sign indicates that the system (the lung) is doing work on the surroundings. We are interested in the magnitude of the work, so the work done is $51\ J$.

Answer:

51 J