Question 1

Which of the following best describes why a steel ship floats on water, even though steel is much denser than water?

Accepted Answer

The density of the ship as a whole (including the air inside) is less than the density of water.

Question 2

A cube of wood with density $$0.6\ \mathrm{g/cm^3$}$$ and volume $$1000\ \mathrm{cm^3$} is $$placed in water (density $$1.0\ \mathrm{g/cm^3$}). $$What is the magnitude of the buoyant force acting on the cube?

Accepted Answer

$$9.8\ \mathrm{N} ($$since the cube displaces $$1.0\ \mathrm{kg} of $$water, $$F_b = \rho_{water} V g)$$

Question 3

Which equation correctly expresses the hydrostatic pressure at a depth $$h$$ below the surface of a fluid of density $$\rho$$?

Accepted Answer

$$P = \rho g h$$

Question 4

A barometer is used to measure atmospheric pressure. If the atmospheric pressure decreases, what happens to the height of the mercury column in the barometer?

Accepted Answer

It decreases.

Question 5

Which of the following statements about Pascal's Principle is correct?

Accepted Answer

A change in pressure applied to an enclosed incompressible fluid is transmitted undiminished to all portions of the fluid and to the walls of its container.

Question 6

A hydraulic lift uses a small piston of area $$A_1$$ and a large piston of area $$A_2. If a $$force $$F_1 is $$applied to the small piston, what is the force $$F_2$$ exerted by the large piston, assuming the fluid is incompressible?

Accepted Answer

$$F_2$$ = $$F_1$$ \frac{$$A_2$$}{$$A_1$$}$$

Question 7

Which of the following best describes the difference between laminar and turbulent flow in fluids?

Accepted Answer

Laminar flow consists of smooth, parallel layers of fluid, while turbulent flow is chaotic and irregular.

Question 8

The Reynolds number $$Re is $$given by $$Re = \frac{\rho v L}{\eta}$$, where $$\rho is $$fluid density, $$v is $$velocity, $$L is $$characteristic length, and $$\eta is $$viscosity. What does a large Reynolds number indicate?

Accepted Answer

The flow is likely to be turbulent.

Question 9

According to the equation of continuity for an incompressible fluid, $$A_1$$ $$v_1$$ = $$A_2$$ $$v_2. If $$the cross-sectional area of a pipe decreases, what happens to the speed of the fluid?

Accepted Answer

The speed increases.

Question 10

Bernoulli's equation for a streamline is $$P + \frac{1}{2}ho v^2$ + ho g h = 	ext{constant}. $$Which of the following is a correct implication of this equation?

Accepted Answer

Where the fluid speed increases, the pressure decreases.

Question 11

A Venturi tube is used to measure the speed of a fluid. If the cross-sectional area narrows, what happens to the pressure and speed of the fluid in the narrow section?

Accepted Answer

Pressure decreases, speed increases.

Question 12

Which of the following is the correct expression for the root-mean-square speed $$v_{rms} of a $$gas molecule at temperature $$T$$?

Accepted Answer

$$v_{rms} = \sqrt{\frac{3 k_B T}{m}}$$

Question 13

Which of the following factors will NOT increase the pressure of an ideal gas in a sealed container?

Accepted Answer

Increasing the volume of the container.

Question 14

A U-shaped tube is filled with water and oil (density $$0.8\ \mathrm{g/cm^3$}). If $$the water column is $$10\ \mathrm{cm}$$ high, what is the height of the oil column needed to balance the water column?

Accepted Answer

$$12.5\ \mathrm{cm}$$

Question 15

Which of the following best explains why atmospheric pressure decreases with increasing altitude?

Accepted Answer

There are fewer air molecules above a given point as altitude increases.

Question 16

Which of the following is the correct form of Poiseuille's Law for the volume flow rate $$Q of a $$viscous fluid through a tube of radius $$r$$ and length $$l$$ under pressure difference $$\Delta P$$?

Accepted Answer

$$Q = \frac{\pi r^4$ \Delta P}{8 \eta l}$$

Question 17

Which of the following statements about surface tension is correct?

Accepted Answer

Surface tension is caused by cohesive forces between molecules at the surface of a liquid.

Question 18

A capillary tube is placed vertically in water. The water rises in the tube due to capillary action. Which property of water is primarily responsible for this phenomenon?

Accepted Answer

Adhesion between water molecules and the glass.

Question 19

Which of the following best describes the physical meaning of the equation $$P = F/A$$?

Accepted Answer

Pressure is the force applied per unit area.

Fluids: Properties, Pressure, and Fluid Dynamics

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