BIO. 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. (a) What is the lowest gauge pressure that the average person can achieve inside his lungs? (b) Explain why your answer in part (a) is negative.

At point A, a hose ejects water at a speed of $5.10\text{ m/s}$. Point B is upstream from, and 30.0cm above, the outlet. If the water is moving at $2.40\text{ m/s}$at point B, what is the internal pressure of the water at B? Use $101.3\text{kPa}$ for atmospheric pressure and $1000{\text{kg/m}}^3$ for the density of water.

The pressure gradient in a pipe carrying water is $600\mathrm{Pa}/\mathrm{m}.$ What pressure gradient would be required to maintain the same flow rate in the same pipe if it were carrying olive oil? Treat the flow as the flow of a viscous fluid. The viscosity of water is $1.0\times {10}^{-3}\mathrm{Pa}\cdot \mathrm{s}$ and the viscosity of olive oil is $8.2\times {10}^{-2}\mathrm{Pa}\cdot \mathrm{s}$.

Suppose the average speed of blood in the aorta is $0.26\text{ m/s}$, and the diameter is 2.0 cm. What is the pressure gradient in this aorta due to the viscosity of blood (assume a human body temperature)?

Exploring Venus. The surface pressure on Venus is 92 atm, and the acceleration due to gravity there is 0.894g. In a future exploratory mission, an upright cylindrical tank of benzene is sealed at the top but still pressurized at 92 atm just above the benzene. The tank has a diameter of 1.72 m, and the benzene column is 11.50 m tall. Ignore any effects due to the very high temperature on Venus. (b) What force does the Venusian atmosphere exert on the outside surface of the bottom of the tank?

A closed container is partially filled with water. Initially, the air above the water is at atmospheric pressure (1.01×10^5 Pa) and the gauge pressure at the bottom of the water is 2500 Pa. Then additional air is pumped in, increasing the pressure of the air above the water by 1500 Pa. (a) What is the gauge pressure at the bottom of the water?

A barrel contains a 0.120-m layer of oil floating on water that is 0.250 m deep. The density of the oil is 600 kg/m^3. (a) What is the gauge pressure at the oil–water interface? (b) What is the gauge pressure at the bottom of the barrel?

Oceans on Mars. Scientists have found evidence that Mars may once have had an ocean 0.500 km deep. The acceleration due to gravity on Mars is 3.71 m/s^2. (a) What would be the gauge pressure at the bottom of such an ocean, assuming it was freshwater? (b) To what depth would you need to go in the earth's ocean to experience the same gauge pressure?