Q: A diver descends to a depth of 20 meters in seawater (density $$\rho = 1025\ \mathrm{kg/m^3$}). $$What is the pressure exerted by the water alone at this depth? (Assume $$g = 9.8\ \mathrm{m/s^2$}$$ and atmospheric pressure is not included.)

$$P = 2.01 \times 10^5$\ \mathrm{Pa}$$

Question 1

A diver descends to a depth of 20 meters in seawater (density $$\rho = 1025\ \mathrm{kg/m^3$}). $$What is the pressure exerted by the water alone at this depth? (Assume $$g = 9.8\ \mathrm{m/s^2$}$$ and atmospheric pressure is not included.)

Accepted Answer

$$P = 2.01 	imes 10^5$\ \mathrm{Pa}$$

Question 2

Which of the following best describes Pascal’s Principle?

Accepted Answer

Pressure applied to an enclosed fluid is transmitted undiminished to every part of the fluid and the walls of the container.

Question 3

A manometer contains water and shows a height difference of $$h = 0.15\ \mathrm{m}$$ between the two arms. What is the pressure difference between the two connected gas bulbs? ($$\rho_{water} = 1000\ \mathrm{kg/m^3$}$$, $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$\Delta P = 1470\ \mathrm{Pa}$$

Question 4

Which of the following statements about surface tension is correct?

Accepted Answer

Surface tension is the force per unit length acting along the surface of a liquid.

Question 5

A soap film is stretched across a frame with a movable wire of width $$w = 0.04\ \mathrm{m}. If a $$force of $$F = 6.0\ \mathrm{mN} is $$required to hold the wire steady, what is the surface tension of the soap solution? (Remember there are two surfaces.)

Accepted Answer

$$\gamma = 0.075\ \mathrm{N/m}$$

Question 6

Why are surfactants crucial for proper lung function, especially in premature infants?

Accepted Answer

They reduce surface tension in alveoli, preventing collapse and stabilizing air sacs of different sizes.

Question 7

A blood vessel narrows so that its radius decreases by 20%. By what factor does the volume flow rate change, assuming all other factors remain constant? (Use Poiseuille’s Law: $$F \propto r^4$)

Accepted Answer

The flow rate decreases to about 41% of its original value.

Question 8

Which of the following best describes capillary action?

Accepted Answer

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

Question 9

A pipe carrying water narrows from a cross-sectional area $$A_1 = 0.02$$\ \mathrm{$$m^2$$}$$ to A_2$ = 0.01\ \mathrm{m^2$}. If $$the velocity in the wider section is $$v_1 = 2$$\ \mathrm{m/s}$$, what is the velocity in the narrower section? (Use the continuity equation: A_1$ v_1$ = A_2$ v_2$)

Accepted Answer

$$v_2 = 4$$\ \mathrm{m/s}$$

Question 10

According to Bernoulli’s equation, what happens to the pressure in a fluid as its velocity increases (assuming constant height and negligible viscosity)?

Accepted Answer

The pressure decreases.

Question 11

Which of the following is NOT a condition for Bernoulli’s equation to be valid?

Accepted Answer

The fluid must be compressible.

Question 12

A large artery in a dog has an inner radius of $$4 	imes 10$$^{-3}$$\ \mathrm{m}$$ and blood flows through it at a rate of $$10^{-6}$$\ \mathrm{$$m^3/s$$}$$. What is the average velocity of the blood in the artery?

Accepted Answer

$$v = 20\ \mathrm{m/s}$$

Question 13

Which of the following best describes turbulent flow?

Accepted Answer

Fluid motion is irregular, with mixing between layers and eddy currents.

Question 14

Which device is commonly used to measure blood pressure in the human body?

Accepted Answer

Sphygmomanometer

Question 15

If the pressure in a fluid at a certain depth is $$P = P_0$ + \rho g h$$, what does each symbol represent?

Accepted Answer

$$P_0 is $$the pressure at the surface, $$\rho is $$the fluid density, $$g is $$acceleration due to gravity, $$h is $$the depth.

Question 16

Which of the following is a real-life example of capillary action?

Accepted Answer

The rise of water in the thin tubes of plant roots and stems.

Question 17

Which of the following statements about blood flow in arteries is correct?

Accepted Answer

A small decrease in artery radius greatly reduces blood flow due to the $$r^4$$ dependence in Poiseuille’s Law.

Question 18

Which of the following best explains why a needle can float on water but sinks when soap is added?

Accepted Answer

Soap reduces the surface tension of water, so the needle is no longer supported.

Question 19

Which of the following is NOT a type of fluid flow described in the study materials?

Accepted Answer

Rotational flow

Fluid Mechanics in Biological Systems: Pressure, Flow, and Applications

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