Exam 11: Static Fluids

Which of these statements best describes the reason that fish can float in water?

What is the diameter of a capillary tube holding methanol, if the methanol rises to the same height as water in a 1 mm diameter tube? (Take 0° for contact angles, surface tension for water ó_H2O= 0.073 N/m, and of methanol ó_methanol = 0.023 N/m. Density of water is ñ_H2O = 1000 kg/m³, and of methanol ñ_methanol = 792 kg/m³.)

Describe the position of a human body in which all the gauge pressures in the cardiovascular system are positive, and another position where you can expect negative gauge pressure to occur.

The fisher spider (Dolomedes triton), with mass of 0.7 g, walks on the water with eight legs. What length of each leg is in contact with the water so that the spider stays on the surface? Ignore the width of the leg; take into account only that each leg has two sides in contact with water. The surface tension of water is ó = 0.073 N/m.

The ideal stationary fluid is incompressible. This means you cannot deform it. If you act on such a fluid to deform it, it responds with a change in density.

A bucket of water has some ice floating in it. When water freezes into ice, the ice becomes less dense than water, and about 9% of ice volume is above the water. When the ice melts, what happens to the level of water in the bucket?

Figure 11.1 -Dolphins are sleeping at the bottom of a cove, floating low above the ocean floor. Which diagram in Fig. 11.1 shows the correct forces acting on the dolphins?

Calculate the pressure in a water bubble of diameter 0.04 cm, and compare that with the pressure in the same diameter bubble of water-and-surfactant, which reduces surface tension by half. The surface tension of water is ó = 0.073 N/m.

If P is a pressure, ñ density, g gravitational acceleration, and h height (or depth) of a fluid, where is the relationship P = ñgh applicable?

If, in an unknown liquid, we measure pressure of 1.2 atm at 0.15 m depth, at what depth will the pressure measure 2.4 atm?

Surface tension is a force per unit area of the surface of a liquid.

If the height of a column of mercury supported by a blood pressure of 0.16 Pa is 120 mm, what height would a column of water be if you used a water manometer to measure the same pressure? (Note: The density of mercury is ñ = 1.36 × 10⁴ kg/m³, and the density of water is ñ = 10³ kg/m³.)

Major cargo ships sail up the Saint Lawrence Seaway from the Atlantic Ocean to the Great Lakes. If their ballast tanks are not adjusted, the ships will sink lower when they move from the ocean to the fresh-water seaway.

A shark has to swim constantly all its life to prevent its body from sinking because it is heavier than other types of fish.

You have a fluid in a beaker, but you need to increase the density of the contents of the beaker. How can you obtain higher density?

How far below the surface of water do you need to dive to double the atmospheric pressure? (Note: Atmospheric pressure is P_atm = 1.01 × 10⁵ Pa, and density of water is ñ = 1000 kg/m³.)

Use Pascal's law to determine the height of Earth's atmosphere. Compare the result to the height of Mount Everest, h = 8848 m. The real height of the atmosphere is about 500 km. What assumption in Pascal's law is the reason for this difference in results? (Note: Atmospheric pressure is P_atm = 1.01 × 10⁵ Pa, and density of air ñ = 1.2 kg/m³.)

In a weightless environment such as on the International Space Station, water assumes the shape of a sphere.

What percent of the weight of a ship's load has to be removed from a fully laden ship when it enters from the ocean into the St. Lawrence River? (Note: The density of sea water is ñ = 1.025 × 10³ kg/m³, and the density of fresh water is ñ = 10³ kg/m³.)

At the surface of a fluid, the upward force from the fluid equals atmospheric pressure.