Answer
(a) The gauge pressure in the lungs is $-1.1\times 10^4~N/m^2$.
(b) The gauge pressure is negative because in order to make the liquid rise higher in the straw, the pressure in the lungs must be lower than the atmospheric pressure.
Work Step by Step
The gauge pressure in a person's lungs is equal in magnitude to the gauge pressure of water at a depth of 1.1 meters.
$P_G = -\rho~g~h$
$P_G = -(1000~kg/m^3)(9.80~m/s^2)(1.1~m)$
$P_G = -1.1\times 10^4~N/m^2$
The gauge pressure in the lungs is $-1.1\times 10^4~N/m^2$.
(b) Note that the gauge pressure is negative because in order to make the liquid rise higher in the straw, the pressure in the lungs must be lower than the atmospheric pressure.
