Q: A barometer uses mercury to measure atmospheric pressure. If the atmospheric pressure is $$1.01 \times 10^5$ \ \mathrm{Pa}$$, what is the height $$h of $$the mercury column? (Density of mercury $$= 13,600 \ \mathrm{kg/m^3$}$$, $$g = 9.8 \ \mathrm{m/s^2$})$$

$$h = \frac{1.01 \times 10^5$}{13,600 \times 9.8} \approx 0.76 \ \mathrm{m}$$

Q: A table tennis ball with a density of $$0.0840 \ \mathrm{g/cm^3$}$$ floats in water. What percentage of its volume is submerged?

$$\frac{0.0840}{1.00} \times 100\% = 8.40\%$$

Question 1

Which of the following best describes the difference between a liquid and a gas in terms of compressibility?

Accepted Answer

Liquids are nearly incompressible, while gases are compressible.

Question 2

A sample of water at 4°C has a density of $$1.00 	imes 10^3$ \ \mathrm{kg/m^3$}. $$What is the specific gravity of seawater with a density of $$1030 \ \mathrm{kg/m^3$}$$?

Accepted Answer

$$SG = \frac{1030}{1000} = 1.03$$

Question 3

Which statement about pressure in a fluid at rest is correct?

Accepted Answer

Pressure increases with depth and is the same at all points on a horizontal line at a given depth.

Question 4

A barometer uses mercury to measure atmospheric pressure. If the atmospheric pressure is $$1.01 	imes 10^5$ \ \mathrm{Pa}$$, what is the height $$h of $$the mercury column? (Density of mercury $$= 13,600 \ \mathrm{kg/m^3$}$$, $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$h = \frac{1.01 	imes 10^5$}{13,600 	imes 9.8} \approx 0.76 \ \mathrm{m}$$

Question 5

A hydraulic lift uses Pascal’s principle. If a force of $$500 \ \mathrm{N} is $$applied to a piston of area $$0.01 \ \mathrm{m^2$}$$, what is the pressure transmitted to a second piston of area $$0.1 \ \mathrm{m^2$}$$?

Accepted Answer

$$P = \frac{500}{0.01} = 50,000 \ \mathrm{Pa}$$

Question 6

A person with a body density of $$990 \ \mathrm{kg/m^3$}$$ floats in water. What fraction of their body is submerged?

Accepted Answer

$$\frac{990}{1000} = 0.99$$

Question 7

Which of the following best explains why a balloon filled with helium floats in air?

Accepted Answer

Helium is less dense than air, so the buoyant force exceeds the weight of the balloon.

Question 8

A U-shaped open-tube manometer contains water. If the pressure in the left arm is $$p_1$$ and the right arm is open to the atmosphere ($$p_0$$), and the water column is higher on the left, what is the gauge pressure?

Accepted Answer

$$p_g = p_1$ - p_0$

Question 9

A table tennis ball with a density of $$0.0840 \ \mathrm{g/cm^3$}$$ floats in water. What percentage of its volume is submerged?

Accepted Answer

$$\frac{0.0840}{1.00} 	imes 100\% = 8.40\%$$

Question 10

Which of the following is true about surface tension?

Accepted Answer

Surface tension is caused by cohesive forces between molecules at the liquid’s surface.

Question 11

A soap bubble has two surfaces. What is the excess pressure inside the bubble compared to outside, given surface tension $$\gamma$$ and radius $$R$$?

Accepted Answer

$$\Delta p = \frac{4\gamma}{R}$$

Question 12

Which of the following best describes capillary action?

Accepted Answer

It is the rise or fall of liquid in a narrow tube due to adhesive and cohesive forces.

Question 13

Water flows through a pipe that narrows from area $$A_1 to$$ $$A_2. If $$the speed at $$A_1 is$$ $$v_1$$, what is the speed at $$A_2$$ according to the continuity equation?

Accepted Answer

$$v_2$$ = \frac{$$A_1$$}{$$A_2$$} $$v_1$$

Question 14

According to Bernoulli’s equation, what happens to the pressure in a fluid as its speed increases?

Accepted Answer

Pressure decreases as speed increases.

Question 15

A prairie dog burrow has two entrances at different heights. When wind blows across the mounds, air flows through the burrow. Which principle explains this ventilation?

Accepted Answer

Bernoulli’s effect: lower pressure at the higher mound causes air to flow toward it.

Question 16

Blood flows through an artery of radius $$r$$ and length $$L. $$According to Poiseuille’s equation, how does the flow rate $$Q$$ change if the radius is halved?

Accepted Answer

Flow rate decreases by a factor of 16.

Question 17

Which of the following is true about the flow speed of blood in the circulatory system?

Accepted Answer

Flow speed decreases as blood moves from large arteries to capillaries due to increased total cross-sectional area.

Question 18

A nurse measures blood pressure with a cuff at the level of the patient’s heart. If the cuff is raised above heart level, what happens to the measured pressure?

Accepted Answer

The measurement would record a lower pressure.

Fluids: Physics for Life Sciences (Chapter 9) - Structured Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards