# Problem: The lower end of a long plastic straw is immersed below the surface of the water in a plastic cup. An average person sucking on the upper end of the straw can pull water into the straw to a vertical height of 1.1 m above the surface of the water in the cup. What is the lowest gauge pressure that the average person can achieve inside his lungs?

###### FREE Expert Solution

Gauge pressure is given by:

$\overline{){\mathbf{P}}{\mathbf{=}}{\mathbf{\rho }}{\mathbf{g}}{\mathbf{h}}}$, where ρ is the density of water, g is the acceleration due to gravity, and h is the vertical height.

Lowest pressure achievable inside the lungs:

$\overline{){{\mathbf{P}}}_{\mathbf{l}\mathbf{u}\mathbf{n}\mathbf{g}\mathbf{s}}{\mathbf{=}}{{\mathbf{P}}}_{{\mathbf{0}}}{\mathbf{+}}{\mathbf{P}}}$, where P0 is atmospheric pressure.

###### Problem Details

The lower end of a long plastic straw is immersed below the surface of the water in a plastic cup. An average person sucking on the upper end of the straw can pull water into the straw to a vertical height of 1.1 m above the surface of the water in the cup. What is the lowest gauge pressure that the average person can achieve inside his lungs?