Q: A barometer is used to measure atmospheric pressure. If the height of the mercury column is $$0.76 \ \mathrm{m}$$ and the density of mercury is $$13,600 \ \mathrm{kg/m^3$}$$, what is the atmospheric pressure? (Take $$g = 9.8 \ \mathrm{m/s^2$})$$

$$1.01 \times 10^5$ \ \mathrm{N/m^2$}$$

Q: A submarine is at a depth of $$200 \ \mathrm{m} in $$seawater ($$\rho = 1025 \ \mathrm{kg/m^3$}). $$What is the absolute pressure at this depth? (Atmospheric pressure $$P_{atm} = 1.01 \times 10^5$ \ \mathrm{N/m^2$}$$, $$g = 9.8 \ \mathrm{m/s^2$})$$

$$2.11 \times 10^6$ \ \mathrm{N/m^2$}$$

Question 1

A block of wood with a density of $$600 \ \mathrm{kg/m^3$} is $$placed in water ($$\rho_{water} = 1000 \ \mathrm{kg/m^3$}). $$What fraction of the block's volume will be submerged when it floats in equilibrium?

Accepted Answer

$$0.60$$

Question 2

Which of the following best explains why ice floats on water?

Accepted Answer

Ice is less dense than liquid water because its molecules are arranged in a more open structure.

Question 3

A dam is designed to hold back water in a reservoir. Why must the base of the dam be thicker than the top?

Accepted Answer

Pressure increases with depth, so the force on the dam is greatest at the bottom.

Question 4

A hydraulic lift uses Pascal's Principle to lift a car. If the input piston has an area of $$0.01 \ \mathrm{m^2$}$$ and the output piston has an area of $$1.0 \ \mathrm{m^2$}$$, what force must be applied to the input piston to lift a $$10,000 \ \mathrm{N}$$ car?

Accepted Answer

$$100 \ \mathrm{N}$$

Question 5

A barometer is used to measure atmospheric pressure. If the height of the mercury column is $$0.76 \ \mathrm{m}$$ and the density of mercury is $$13,600 \ \mathrm{kg/m^3$}$$, what is the atmospheric pressure? (Take $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$1.01 	imes 10^5$ \ \mathrm{N/m^2$}$$

Question 6

A pipe narrows from a cross-sectional area of $$0.05 \ \mathrm{m^2$} to$$ $$0.01 \ \mathrm{m^2$}. If $$the velocity of water in the wider section is $$2 \ \mathrm{m/s}$$, what is the velocity in the narrower section? (Assume incompressible flow.)

Accepted Answer

$$10 \ \mathrm{m/s}$$

Question 7

Which equation correctly expresses Bernoulli's Principle for a fluid flowing horizontally with no change in height?

Accepted Answer

$$P_1$$ + \frac{1}{2} \rho $$v_1^2$$ = $$P_2$$ + \frac{1}{2} \rho $$v_2^2$

Question 8

A cube of side $$0.2 \ \mathrm{m} is $$completely submerged in water. What is the magnitude of the buoyant force acting on the cube? (Take $$\rho_{water} = 1000 \ \mathrm{kg/m^3$}$$, $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$78.4 \ \mathrm{N}$$

Question 9

If a hole is punched in the side of an open water tank at a depth $$h$$ below the surface, what is the speed of the water as it exits the hole? (Neglect viscosity and air resistance.)

Accepted Answer

$$v = \sqrt{2gh}$$

Question 10

A patient’s blood flows from a wider artery ($$A_1 = 2$$ \ \mathrm{$$cm^2$$}$$, v_1$ = 0.2 \ \mathrm{m/s}) $$into a narrower capillary ($$A_2 = 0.5$$ \ \mathrm{$$cm^2$$}$$). What is the velocity of blood in the capillary?

Accepted Answer

$$0.8 \ \mathrm{m/s}$$

Question 11

Which of the following statements about pressure in a static fluid is correct?

Accepted Answer

Pressure at a given depth is the same in all directions.

Question 12

A submarine is at a depth of $$200 \ \mathrm{m} in $$seawater ($$ho = 1025 \ \mathrm{kg/m^3$}). $$What is the absolute pressure at this depth? (Atmospheric pressure $$P_{atm} = 1.01 	imes 10^5$ \ \mathrm{N/m^2$}$$, $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$2.11 	imes 10^6$ \ \mathrm{N/m^2$}$$

Question 13

Which of the following is a direct application of Archimedes’ Principle in medicine?

Accepted Answer

Measuring body fat percentage using water displacement.

Question 14

A concrete boat floats because:

Accepted Answer

It displaces a volume of water whose weight equals the total weight of the boat, including air pockets.

Question 15

If the velocity of a fluid increases as it flows through a constriction, what happens to the pressure according to Bernoulli’s equation?

Accepted Answer

The pressure decreases.

Question 16

A weather balloon is released and rises through the atmosphere. As it rises, the external pressure decreases. What happens to the volume of the balloon (assuming temperature is constant)?

Accepted Answer

The volume increases.

Question 17

Which of the following best describes why you are able to drink through a straw?

Accepted Answer

Atmospheric pressure pushes the liquid up the straw when you reduce the pressure in your mouth.

Question 18

A fluid flows from point 1 to point 2 in a horizontal pipe. If $$v_2$$ \u003e $$v_1$$, what can you say about the pressures $$P_1$$ and $$P_2$$?

Accepted Answer

$$P_1$$ \u003e $$P_2$$

Question 19

A patient’s IV bag is raised higher above the arm to increase the flow rate. Which principle explains why this works?

Accepted Answer

Increasing the height increases the pressure difference, causing fluid to flow faster.

Fluids: Density, Pressure, Buoyancy, and Fluid Dynamics (PHYS 111 Study Notes)

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