Q: What is the SI unit for pressure, and how is it defined?

Pascal (Pa), defined as $$1 \ \text{N/m}^2$$

Question 1

Which of the following best describes the difference in density between solids, liquids, and gases, as illustrated in the provided diagram?

Accepted Answer

Gases have the lowest density because their molecules are far apart and contain more empty space.

Question 2

A 250 mL cup is filled with water and then with blood. Which property explains why the mass is different for each substance?

Accepted Answer

The density of the substances.

Question 3

What is the SI unit for pressure, and how is it defined?

Accepted Answer

Pascal (Pa), defined as $$1 \ 	ext{N/m}^2$$

Question 4

Which equation correctly defines mass density ($$\rho) $$for a homogeneous material?

Accepted Answer

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

Question 5

A diver descends to a depth $$h in $$water. Which formula gives the pressure at that depth, assuming atmospheric pressure is $$P_0$$ and water density is $$\rho$$?

Accepted Answer

$$P = P_0$ + \rho g h$$

Question 6

Which statement best explains why atmospheric pressure decreases with altitude?

Accepted Answer

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

Question 7

A mercury barometer is used to measure atmospheric pressure. What does the height of the mercury column represent?

Accepted Answer

The atmospheric pressure exerted on the mercury reservoir.

Question 8

Blood pressure is often measured in mm Hg. If a reading is 130/80, what does this represent?

Accepted Answer

The maximum and minimum gauge pressures in the arteries.

Question 9

Which principle states that pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and the walls of the container?

Accepted Answer

Pascal's principle

Question 10

A hydraulic lift uses Pascal’s principle. If a force $$F_1 is $$applied to a small piston of area $$A_1$$, and a larger piston of area $$A_2$$ lifts a car, which equation relates the forces and areas?

Accepted Answer

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

Question 11

Which of the following best describes gauge pressure?

Accepted Answer

Gauge pressure is the difference between absolute pressure and atmospheric pressure.

Question 12

A block of wood floats in water. According to Archimedes’ principle, what is true about the buoyant force acting on the block?

Accepted Answer

The buoyant force equals the weight of the water displaced by the block.

Question 13

A cube of ice with mass $$m$$ and volume $$V is $$placed in water. If the density of ice is $$\rho_{ice}$$ and water is $$\rho_{water}$$, which condition must be true for the ice to float?

Accepted Answer

$$\rho_{ice} \u003c \rho_{water}$$

Question 14

A swimmer dives to a depth of 5 m in a lake. If the density of water is $$1000 \ 	ext{kg/m}^3$$ and $$g = 9.8 \ 	ext{m/s}^2$$, what is the increase in pressure due to the water at this depth?

Accepted Answer

$$49,000 \ 	ext{Pa}$$

Question 15

Which of the following is NOT a consequence of Pascal’s principle in real-world applications?

Accepted Answer

Floating objects

Question 16

If a pressure gauge reads 50 kPa and the atmospheric pressure is 101 kPa, what is the absolute pressure?

Accepted Answer

$$151 \ 	ext{kPa}$$

Question 17

A submerged object experiences a net upward force. What is the physical origin of this force?

Accepted Answer

The difference in pressure between the top and bottom of the object.

Question 18

Which equation expresses the buoyant force ($$F_b) $$acting on a submerged object of volume $$V in a $$fluid of density $$\rho$$?

Accepted Answer

$$F_b = \rho V g$$

Question 19

A patient’s blood pressure is measured at the upper arm, level with the heart. Why is this location used as a standard reference?

Accepted Answer

Because blood pressure varies with vertical position in the body.

Fluid Mechanics: Density, Pressure, and Buoyancy

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