Q: The specific gravity of a material is defined as:

$$\text{Specific gravity} = \frac{\rho_{\text{material}}}{\rho_{\text{water @ 4^\circ C}}}$$

Q: A swimmer’s hand has a surface area of $$8.4 \times 10$$^{-3}$$\ \mathrm{m^2$}$$ and experiences a pressure of $$1.2 \times 10^5$\ \mathrm{Pa}. $$What is the magnitude of the force acting on the hand?

$$1.0 \times 10^3$\ \mathrm{N}$$

Q: If the atmospheric pressure at the surface of a lake is $$1.01 \times 10^5$\ \mathrm{Pa}$$, the density of water is $$1.000 \times 10^3$\ \mathrm{kg/m^3$}$$, and the depth is $$5.50\ \mathrm{m}$$, what is the pressure at this depth?

$$1.55 \times 10^5$\ \mathrm{Pa}$$

Q: A hydraulic lift uses oil with a density of $$800\ \mathrm{kg/m^3$}. If $$the oil column is $$2.0\ \mathrm{m}$$ high, what is the pressure at the bottom of the column due to the oil alone? (Use $$g = 9.81\ \mathrm{m/s^2$})$$

$$1.57 \times 10^4$\ \mathrm{Pa}$$

Q: If you dive to a depth where the pressure is $$2.5 \times 10^5$\ \mathrm{Pa}$$ and the atmospheric pressure is $$1.0 \times 10^5$\ \mathrm{Pa}$$, what is the gauge pressure at that depth?

$$1.5 \times 10^5$\ \mathrm{Pa}$$

Q: A tank contains two immiscible liquids, oil ($$\rho = 800\ \mathrm{kg/m^3$}) $$floating on water ($$\rho = 1000\ \mathrm{kg/m^3$}). If $$the oil layer is $$1.0\ \mathrm{m}$$ thick and the water layer is $$2.0\ \mathrm{m}$$ thick, what is the total pressure at the bottom of the tank due to both liquids? (Atmospheric pressure is not included.)

$$2.6 \times 10^4$\ \mathrm{Pa}$$

Question 1

Which of the following best describes a fluid in the context of physics?

Accepted Answer

A material that can flow, including liquids, gases, and plasmas.

Question 2

A suitcase is packed with clothes until it is full. If you have two suitcases of different sizes but with the same mass of clothes inside, which suitcase has the higher density?

Accepted Answer

The smaller suitcase.

Question 3

What is the correct formula for the mass density $$\rho of a $$material?

Accepted Answer

$$\rho = \frac{m}{V}$$

Question 4

The specific gravity of a material is defined as:

Accepted Answer

$$	ext{Specific gravity} = \frac{ho_{	ext{material}}}{ho_{	ext{water @ 4^\circ C}}}$$

Question 5

If the density of water at $$4^\circC is$$ $$1.000 	imes 10^3$\ \mathrm{kg/m^3$}$$, what is the specific gravity of mercury with a density of $$13,600\ \mathrm{kg/m^3$}$$?

Accepted Answer

13.6

Question 6

Which of the following statements about pressure is correct?

Accepted Answer

Pressure is defined as the magnitude of the average force applied perpendicularly over an area.

Question 7

A swimmer’s hand has a surface area of $$8.4 	imes 10$$^{-3}$$\ \mathrm{m^2$}$$ and experiences a pressure of $$1.2 	imes 10^5$\ \mathrm{Pa}. $$What is the magnitude of the force acting on the hand?

Accepted Answer

$$1.0 	imes 10^3$\ \mathrm{N}$$

Question 8

Which equation correctly relates the pressure at two different depths in a fluid?

Accepted Answer

$$P_2$$ = $$P_1$$ + \rho g h$$

Question 9

If the atmospheric pressure at the surface of a lake is $$1.01 	imes 10^5$\ \mathrm{Pa}$$, the density of water is $$1.000 	imes 10^3$\ \mathrm{kg/m^3$}$$, and the depth is $$5.50\ \mathrm{m}$$, what is the pressure at this depth?

Accepted Answer

$$1.55 	imes 10^5$\ \mathrm{Pa}$$

Question 10

Why does pressure at a given depth in a fluid not depend on the shape of the container?

Accepted Answer

Because pressure at a given depth depends only on the height of the fluid column above that point, not the container’s shape.

Question 11

A hydraulic lift uses oil with a density of $$800\ \mathrm{kg/m^3$}. If $$the oil column is $$2.0\ \mathrm{m}$$ high, what is the pressure at the bottom of the column due to the oil alone? (Use $$g = 9.81\ \mathrm{m/s^2$})$$

Accepted Answer

$$1.57 	imes 10^4$\ \mathrm{Pa}$$

Question 12

Which of the following is NOT a fluid according to the physics definition?

Accepted Answer

A block of ice at $$-10^\circC$$

Question 13

If you dive to a depth where the pressure is $$2.5 	imes 10^5$\ \mathrm{Pa}$$ and the atmospheric pressure is $$1.0 	imes 10^5$\ \mathrm{Pa}$$, what is the gauge pressure at that depth?

Accepted Answer

$$1.5 	imes 10^5$\ \mathrm{Pa}$$

Question 14

A tank contains two immiscible liquids, oil ($$\rho = 800\ \mathrm{kg/m^3$}) $$floating on water ($$\rho = 1000\ \mathrm{kg/m^3$}). If $$the oil layer is $$1.0\ \mathrm{m}$$ thick and the water layer is $$2.0\ \mathrm{m}$$ thick, what is the total pressure at the bottom of the tank due to both liquids? (Atmospheric pressure is not included.)

Accepted Answer

$$2.6 	imes 10^4$\ \mathrm{Pa}$$

Question 15

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

Accepted Answer

There is less air (and thus less weight of air) above you as you go higher.

Question 16

A scuba diver descends to a depth where the water pressure is $$3.0 	imes 10^5$\ \mathrm{Pa}. If $$the diver’s body presents a surface area of $$0.50\ \mathrm{m^2$}$$, what is the total force exerted by the water on that area?

Accepted Answer

$$1.5 	imes 10^5$\ \mathrm{N}$$

Question 17

Which of the following is the SI unit for pressure?

Accepted Answer

$$\mathrm{Pa} ($$Pascal)

Question 18

If the density of a gas increases while temperature and gravity remain constant, what happens to the pressure at a given depth?

Accepted Answer

The pressure increases.

Fluids: Properties, Pressure, and Depth in Physics- lecture 20

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