Q: A force of $$2.6 \ \mathrm{N} is $$applied to a balloon with a fingertip area of $$1.5 \times 10$$^{-4}$$ \ \mathrm{m^2$}. $$What is the pressure exerted on the balloon?

$$1.73 \times 10$$^{4}$$ \ \mathrm{N/m^2$}$$

Q: A submarine is at a depth of $$3,500 \ \mathrm{m} in $$seawater ($$\rho = 1,025 \ \mathrm{kg/m^3$}). $$What is the gauge pressure at this depth? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

$$3.52 \times 10^7$ \ \mathrm{N/m^2$}$$

Question 1

Which of the following best describes why gases are considered fluids, but solids are not?

Accepted Answer

Gases can flow and take the shape of their container, while solids are rigid and have a fixed shape.

Question 2

A refrigerator has internal dimensions of 1.0 m × 0.61 m × 0.75 m. If the density of air is $$1.29 \ \mathrm{kg/m^3$}$$, what is the mass of air inside the refrigerator?

Accepted Answer

$$0.59 \ \mathrm{kg}$$

Question 3

Which equation correctly defines density?

Accepted Answer

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

Question 4

A force of $$2.6 \ \mathrm{N} is $$applied to a balloon with a fingertip area of $$1.5 	imes 10$$^{-4}$$ \ \mathrm{m^2$}. $$What is the pressure exerted on the balloon?

Accepted Answer

$$1.73 	imes 10$$^{4}$$ \ \mathrm{N/m^2$}$$

Question 5

If a balloon pops at a pressure of $$3.7 	imes 10^5$ \ \mathrm{N/m^2$}$$ and the needle tip area is $$2.3 	imes 10$$^{-7}$$ \ \mathrm{m^2$}$$, what is the minimum force needed to pop the balloon?

Accepted Answer

$$0.0851 \ \mathrm{N}$$

Question 6

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

Accepted Answer

Pressure in a fluid acts equally in all directions and at right angles to any surface.

Question 7

A hydraulic lift has a small piston of radius $$4.5 \ \mathrm{cm}$$ and a large piston of radius $$18 \ \mathrm{cm}. If a $$mechanic wants to lift a $$21,000 \ \mathrm{N}$$ truck, what force must be applied to the small piston? (Assume $$A = \pi r^2$)

Accepted Answer

$$1,312.5 \ \mathrm{N}$$

Question 8

Which equation gives the pressure at a depth $$h in a $$fluid of density $$\rho$$ under atmospheric pressure $$P_0$$?

Accepted Answer

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

Question 9

A submarine is at a depth of $$3,500 \ \mathrm{m} in $$seawater ($$\rho = 1,025 \ \mathrm{kg/m^3$}). $$What is the gauge pressure at this depth? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$3.52 	imes 10^7$ \ \mathrm{N/m^2$}$$

Question 10

According to Archimedes’ Principle, the buoyant force on an object submerged in a fluid is equal to:

Accepted Answer

The weight of the fluid displaced by the object

Question 11

A person weighs $$720.0 \ \mathrm{N} in $$air and $$34.3 \ \mathrm{N}$$ when fully submerged in water. What is the volume of the person? (Use $$g = 9.8 \ \mathrm{m/s^2$}$$ and $$\rho_{water} = 1000 \ \mathrm{kg/m^3$})$$

Accepted Answer

$$0.070 \ \mathrm{m^3$}$$

Question 12

If the weight of the water displaced by an object is less than the weight of the object, what will happen?

Accepted Answer

The object will sink.

Question 13

A $$60.0 \ \mathrm{kg}$$ woman floats in freshwater with $$97\% of $$her volume submerged. What is her average density?

Accepted Answer

$$970 \ \mathrm{kg/m^3$}$$

Question 14

Suppose you pour water into a container to a depth of $$14 \ \mathrm{cm}$$, then add $$7.5 \ \mathrm{cm} of $$olive oil ($$\rho = 920 \ \mathrm{kg/m^3$}) on $$top. What is the pressure at the bottom? ($$\rho_{water} = 1000 \ \mathrm{kg/m^3$}$$, $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$2,070 + 1,058 = 3,128 \ \mathrm{Pa}$$

Question 15

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

Accepted Answer

Ice has a lower density than water.

Question 16

A cubical block of wood ($$\rho = 634 \ \mathrm{kg/m^3$}$$, side $$= 13.3 \ \mathrm{cm}) $$floats in water. What volume of water must be displaced for the block to float?

Accepted Answer

The volume equal to the volume of the block times $$\dfrac{\rho_{wood}}{\rho_{water}}$$

Question 17

Which of the following is the best strategy for safely moving off cracking ice?

Accepted Answer

Lie down flat on the ice and crawl toward shore.

Question 18

Which of the following containers filled with water to the same height and base area will have the greatest total force on its base?

Accepted Answer

All containers have the same force on the base.

Fluids: Properties, Pressure, and Buoyancy

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