Q: A force of $$20\ \text{N} is $$applied to a surface area of $$0.05\ \text{m}^2. $$What is the pressure exerted on the surface?

$$P = \frac{F}{A} = \frac{20}{0.05} = 400\ \text{Pa}$$

Q: A diver is at a depth of $$5\ \text{m} in $$freshwater ($$\rho = 1000\ \text{kg/m}^3). $$What is the hydrostatic pressure at that depth? (Use $$g = 9.81\ \text{m/s}^2)$$

$$P_H = \rho \cdot g \cdot h = 1000 \cdot 9.81 \cdot 5 = 49,050\ \text{Pa}$$

Q: An object with volume $$0.003\ \text{m}^3 is $$fully submerged in seawater ($$\rho = 1025\ \text{kg/m}^3). $$What is the buoyant force acting on it? (Use $$g = 9.81\ \text{m/s}^2)$$

$$F_B = \rho_{fluid} \cdot V_{displaced} \cdot g = 1025 \cdot 0.003 \cdot 9.81 = 30.18\ \text{N}$$

Q: A metal object with mass $$2\ \text{kg}$$ and volume $$0.001\ \text{m}^3 is $$placed in water ($$\rho = 1000\ \text{kg/m}^3). $$Will it float or sink? (Use $$g = 9.81\ \text{m/s}^2)$$

It will sink, because its density ($$2000\ \text{kg/m}^3) is $$greater than water's.

Question 1

Which of the following best explains why liquids, unlike gases, have a definite volume but no fixed shape?

Accepted Answer

Liquids have strong intermolecular forces that maintain a fixed volume, but these forces are not strong enough to keep a fixed shape.

Question 2

A block of wood with a density of $$600\ 	ext{kg/m}^3 is $$placed in water ($$ho = 1000\ 	ext{kg/m}^3). $$What will happen to the block?

Accepted Answer

It will float, because its density is less than that of water.

Question 3

A force of $$20\ 	ext{N} is $$applied to a surface area of $$0.05\ 	ext{m}^2. $$What is the pressure exerted on the surface?

Accepted Answer

$$P = \frac{F}{A} = \frac{20}{0.05} = 400\ 	ext{Pa}$$

Question 4

A diver is at a depth of $$5\ 	ext{m} in $$freshwater ($$ho = 1000\ 	ext{kg/m}^3). $$What is the hydrostatic pressure at that depth? (Use $$g = 9.81\ 	ext{m/s}^2)$$

Accepted Answer

$$P_H = ho \cdot g \cdot h = 1000 \cdot 9.81 \cdot 5 = 49,050\ 	ext{Pa}$$

Question 5

In a hydraulic lift, a force of $$60\ 	ext{N} is $$applied to a piston with area $$0.02\ 	ext{m}^2. $$What force is exerted on a second piston with area $$0.10\ 	ext{m}^2$$?

Accepted Answer

$$F_2$$ = $$F_1$$ \cdot \frac{$$A_2$$}{$$A_1$$} = 60 \cdot \frac{0.10}{0.02} = 300\ 	ext{N}$$

Question 6

An object with volume $$0.003\ 	ext{m}^3 is $$fully submerged in seawater ($$ho = 1025\ 	ext{kg/m}^3). $$What is the buoyant force acting on it? (Use $$g = 9.81\ 	ext{m/s}^2)$$

Accepted Answer

$$F_B = ho_{fluid} \cdot V_{displaced} \cdot g = 1025 \cdot 0.003 \cdot 9.81 = 30.18\ 	ext{N}$$

Question 7

A metal object with mass $$2\ 	ext{kg}$$ and volume $$0.001\ 	ext{m}^3 is $$placed in water ($$ho = 1000\ 	ext{kg/m}^3). $$Will it float or sink? (Use $$g = 9.81\ 	ext{m/s}^2)$$

Accepted Answer

It will sink, because its density ($$2000\ 	ext{kg/m}^3) is $$greater than water's.

Question 8

Which statement best describes the effect of surface tension on a water droplet resting on a leaf?

Accepted Answer

Surface tension causes the droplet to form a nearly spherical shape, minimizing surface area.

Question 9

Why can a paperclip float on water even though its density is greater than water's?

Accepted Answer

Surface tension creates a 'skin' on the water that supports the paperclip if placed gently.

Question 10

Which of the following best explains capillary action in a thin glass tube?

Accepted Answer

Adhesion between water and glass pulls water up the tube, while cohesion among water molecules follows, forming a meniscus.

Question 11

A submarine descends to a depth of $$200\ 	ext{m} in $$seawater ($$ho = 1025\ 	ext{kg/m}^3). $$What is the hydrostatic pressure at this depth? (Use $$g = 9.81\ 	ext{m/s}^2)$$

Accepted Answer

$$P_H = ho \cdot g \cdot h = 1025 \cdot 9.81 \cdot 200 = 2,010,450\ 	ext{Pa}$$

Question 12

A hydraulic car jack uses a small piston with area $$0.01\ 	ext{m}^2$$ and a large piston with area $$0.1\ 	ext{m}^2. If a $$mechanic applies a force of $$100\ 	ext{N} to $$the small piston, what force is exerted by the large piston?

Accepted Answer

$$F_2$$ = $$F_1$$ \cdot \frac{$$A_2$$}{$$A_1$$} = 100 \cdot \frac{0.1}{0.01} = 1000\ 	ext{N}$$

Question 13

A swimmer with mass $$70\ 	ext{kg}$$ and volume $$0.07\ 	ext{m}^3 is $$fully submerged in freshwater ($$ho = 1000\ 	ext{kg/m}^3). $$What is the net force acting on the swimmer? (Use $$g = 9.81\ 	ext{m/s}^2)$$

Accepted Answer

Net force = Buoyant force - Weight = $$1000 \cdot 0.07 \cdot 9.81 - 70 \cdot 9.81 = 686.7 - 686.7 = 0\ 	ext{N} ($$neutral buoyancy)

Question 14

Which of the following statements about hydrostatic pressure is correct?

Accepted Answer

Hydrostatic pressure depends only on the depth and density of the fluid, not the shape of the container.

Question 15

A foam ball and a steel ball of equal volume are placed in water. Which statement correctly describes their behavior?

Accepted Answer

The foam ball floats because its density is less than water's; the steel ball sinks because its density is greater.

Question 16

Which scenario best illustrates Pascal’s Principle in action?

Accepted Answer

Pressing the brake pedal in a car transmits pressure through brake fluid to all wheels, applying force simultaneously.

Question 17

Which factor increases the buoyant force on an object submerged in a fluid?

Accepted Answer

Increasing the volume of the object, so more fluid is displaced.

Question 18

A glass capillary tube is placed in water. Which combination of forces causes water to rise up the tube?

Accepted Answer

Adhesion between water and glass, and cohesion among water molecules.

Chapter 13: Liquids – Properties, Principles, and Applications

Guida di studio - Domande di pratica

Study guide - Flashcard