Wolfson Eup3 Ch15 Test Bank - baixardoc

Essential University Physics, 3e (Wolfson)

Chapter 15 Fluid Motion

15.1 Conceptual Questions

1) Fluid fills the container shown in the figure. At which of the indicated points is the pressure

greatest?

A) A

B) B

C) C

D) D

E) The pressure is the same at each of the labeled points.

Answer: EVar: 1

2) At a certain depth in the ocean, the absolute pressure is p. If you go to twice that depth

(treating the water as incompressible)

A) the absolute pressure will be 2p.

B) the absolute pressure will be less than 2p.

C) the absolute pressure will be greater than 2p.

D) the gauge pressure will not change.

E) the gauge pressure will increase but will not double.

Answer: BVar: 1

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3) If you double the pressure on the surface of a can of water, the buoyant force on a stone placed

in that water will

A) increase, but not double.

B) double.

C) decrease, but not by one-half.

D) not change.

Answer: DVar: 1

4) A cup of water containing an ice cube at 0°C is filled to the brim. The tip of the ice cube sticks

out of the surface. As the ice melts, you observe that

A) the cup overflows.

B) the cup might overflow but it depends on the actual mass of the ice cube.

C) the water level remains the same.

D) the water level actually goes down.

E) There is not enough information to answer this question.

Answer: CVar: 1

5) Salt water is more dense than fresh water. A ship floats in both fresh water and salt water.

Compared to the fresh water, the volume of salt water displaced by the ship is

A) greater than the volume of fresh water.

B) less than the volume of fresh water.

C) the same as the volume of fresh water.

Answer: BVar: 1

6) A 50-cm3 block of wood is floating partially submerged in water, and a 50-cm3 block of iron

is totally submerged in water. Which block has the greater buoyant force on it?

A) the wood

B) the iron

C) Both have the same buoyant force.

D) The answer cannot be determined without knowing the densities of the blocks.

Answer: BVar: 1

7) A rock is under water in a shallow lake. As the rock sinks deeper and deeper into water, the

buoyant force on it

A) increases.

B) decreases.

C) remains constant.

Answer: CVar: 1

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8) A piece of wood is floating in a bathtub. A second piece of wood sits on top of the first piece,

and does not touch the water. If the top piece is taken off and placed in the water, what happens

to the water level in the tub?

A) It goes up.

B) It goes down.

C) It does not change.

D) This cannot be determined without knowing the volume of the top piece of wood.

Answer: CVar: 1

9) Water flows through a pipe having a varying width. More water flows per second through the

wide section than through the narrow section because there is more room for it to flow.

A) True

B) False

Answer: BVar: 1

10) As the speed of a moving fluid increases, the pressure in the fluid

A) increases.

B) remains constant.

C) decreases.

D) may increase or decrease, depending on the density of the fluid.

Answer: CVar: 1

11) When you blow some air above the upper face of a paper strip, the paper rises. This occurs

because

A) the air above the upper face of the paper moves faster, which makes the pressure higher than

at the lower face.

B) the air above the upper face of the paper moves faster, which makes the pressure lower than at

the lower face.

C) the air above the upper face of the paper moves faster but the pressure remains constant.

D) the air above the upper face of the paper moves slower, which makes the pressure higher than

at the lower face.

E) the air above the upper face of the paper moves slower, which makes the pressure lower than

at the lower face.

Answer: BVar: 1

12) You are driving a late model convertible car at the 65 mph speed limit with its soft flexible

roof closed up and the windows closed. You observe that the roof

A) bows inward.

B) is no different from when the car was at rest.

C) bows outward.

D) bows inward only when you are driving uphill.

E) bows inward only when you are driving downhill.

Answer: CVar: 1

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15.2 Problems

1) A certain coin has a diameter of 21.21 mm, a thickness of 1.95 mm, and weighs 0.04905 N.

What is its density?

A) 29.1 × 103 kg/m3

B) 7.26 × 103 kg/m3

C) 9.25 × 103 kg/m3

D) 2.31 × 103 kg/m3

E) 71.2 × 103 kg/m3

Answer: BVar: 1

2) What is the radius of a sphere that has a density of 5000 kg/m3 and a mass of 6.00 kg?

A) 4.98 cm

B) 1.27 cm

C) 6.59 cm

D) 1.56 cm

E) 7.22 cm

Answer: CVar: 1

3) A sphere is constructed of two concentric parts. The inner part is a solid sphere of radius 10.0

cm made of a material with density 4000 kg/m3. The outer part is a spherical shell with inner

radius 10.0 cm and outer radius 20.0 cm. The material in the outer shell has a density 9000

kg/m3.

(a) What is the mass of the sphere?

(b) What is the average density of this sphere?

Answer: (a) 281 kg (b) 8.38 × 103 kg/m3

Var: 1

4) One of the dangers of tornados and hurricanes is the rapid drop in air pressure that is

associated with such storms. Assume that the air pressure inside of a sealed house is 1.02 atm

when a hurricane hits. The hurricane rapidly decreases the external air pressure to 0.910 atm. A

square window in an outside wall of the house measures 2.02 m on each side. What net force

(directed outwards) is exerted on this window? (1 atm = 1.01 × 105 Pa.)

A) 4.53 × 104 N

B) 5.14 × 104 N

C) 4.78 × 105 N

D) 5.37 × 105 N

Answer: AVar: 1

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5) A cubical box, 5.00 cm on each side, is immersed in a fluid. The gauge pressure at the top

surface of the box is 594 Pa and the gauge pressure on the bottom surface is 1133 Pa. What is the

density of the fluid?

A) 1000 kg/m3

B) 1100 kg/m3

C) 1220 kg/m3

D) 2340 kg/m3

E) 12,000 kg/m3

Answer: BVar: 1

6) The weight of a car of mass 1.20 × 103 kg is supported equally by the four tires, which are

inflated to the same gauge pressure. What gauge pressure in the tires is required so the area of

contact of each tire with the road is 1.00 × 102 cm2? (1 atm = 1.01 × 105 Pa.)

A) 11.6 × 105 Pa

B) 11.6 × 104 Pa

C) 2.94 × 105 Pa

D) 2.94 × 104 Pa

E) 2.94 × 103 Pa

Answer: CVar: 1

7) On planet X, the absolute pressure at a depth of 2.00 m below the surface of a liquid nitrogen

lake is 5.00 × 105 N/m2. At a depth 5.00 m below the surface, the absolute pressure is 8.00 ×

105 N/m2. The density of liquid nitrogen is 808 kg/m3.

(a) What is the atmospheric pressure on planet X?

(b) What is the acceleration due to gravity on planet X?

Answer: (a) 3.00 × 105 N/m2 (b) 124 m/s2

Var: 1

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8) As shown in the figure, a container has a vertical tube, whose inner radius is 32.00 mm,

connected to it at its side. An unknown liquid reaches level A in the container and level B in the

tube—level A being 5.0 cm higher than level B. The liquid supports a 20.0-cm high column of

oil, between levels B and C, whose density is 460 kg/m3. What is the density of the unknown

liquid?

A) 1800 kg/m3

B) 2000 kg/m3

C) 1400 kg/m3

D) 1600 kg/m3

E) 1700 kg/m3

Answer: AVar: 1

9) In the figure, an open tank contains a layer of oil floating on top of a layer of water (of density

1000 kg/m3) that is 3.0 m thick, as shown. What must be the thickness of the oil layer if the

gauge pressure at the bottom of the tank is to be The density of the oil is 510 kg/

.

Answer: 4.1 mVar: 50+

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10) The small piston of a hydraulic lift has a diameter of 8.0 cm, and its large piston has a

diameter of 40 cm. The lift raises a load of 15,000 N.

(a) Determine the force that must be applied to the small piston.

(b) Determine the pressure applied to the fluid in the lift.

Answer: (a) 600 N (b) 1.2 × 105 PaVar: 1

11) A 12,000-N car is raised using a hydraulic lift, which consists of a U-tube with arms of

unequal areas, filled with incompressible oil and capped at both ends with tight-fitting pistons.

The wider arm of the U-tube has a radius of 18.0 cm and the narrower arm has a radius of 5.00

cm. The car rests on the piston on the wider arm of the U-tube. The pistons are initially at the

same level. What is the initial force that must be applied to the smaller piston in order to start

lifting the car? (For purposes of this problem, you can neglect the weight of the pistons.)

A) 727 N

B) 926 N

C) 2900 N

D) 3330 N

E) 1.20 kN

Answer: BVar: 1

12) A 12,000-N car is raised using a hydraulic lift, which consists of a U-tube with arms of

unequal areas, filled with incompressible oil with a density of 800 kg/m3 and capped at both

ends with tight-fitting pistons. The wider arm of the U-tube has a radius of 18.0 cm and the

narrower arm has a radius of 5.00 cm. The car rests on the piston on the wider arm of the U-tube.

The pistons are initially at the same level. What is the force that must be applied to the smaller

piston in order to lift the car after it has been raised 1.20 m? (For purposes of this problem, you

can neglect the weight of the pistons.)

A) 0.954 kN

B) 1.88 kN

C) 1.96 kN

D) 3.67 kN

E) 1.20 kN

Answer: CVar: 1

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13) The two water reservoirs shown in the figure are open to the atmosphere, and the water has

density 1000 kg/m3. The manometer contains incompressible mercury with a density of 13,600

kg/m3. What is the difference in elevation h if the manometer reading m is 25.0 cm?

A) 1.58 m

B) 4.20 m

C) 3.75 m

D) 3.40 m

E) 3.15 m

Answer: EVar: 1

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14) The two water reservoirs shown in the figure are open to the atmosphere, and the water has

density 1000 kg/m3. The manometer contains incompressible oil with a density of 820 kg/m3.

What is the difference in elevation h if the manometer reading m is 25.0 cm?

A) 0.045 m

B) 0.025 m

C) 0.065 m

D) 0.115 m

E) 0.205 m

Answer: AVar: 1

15) A wooden raft has a mass of 50 kg. When empty it floats in water (density with

69% of its volume submerged. What mass of sand can be put on the raft without it sinking?

Answer: 22 kg Var: 50+

16) A board that is 20.0 cm wide, 5.00 cm thick, and 3.00 m long has a density 350 kg/m3. The

board is floating partially submerged in water of density 1000 kg/m3. What fraction of the

volume of the board is above the surface of the water?

A) 0.350

B) 0.650

C) zero

D) 0.200

E) The answer depends on which edge of the board is vertical.

Answer: BVar: 5

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17) A rock is suspended from a scale reads 20.0 N. A beaker of water (having a density of 1000

kg/m3) is raised up so the rock is totally submerged in the water. The scale now reads 12.5 N.

What is the density of the rock?

A) 1.60 × 103 kg/m3

B) 2.50 × 103 kg/m3

C) 2.33 × 103 kg/m3

D) 3.00 × 103 kg/m3

E) 2.67 × 103 kg/m3

Answer: EVar: 1

18) A person who weighs 550 N empties her lungs as much as possible and is then completely

immersed in water (of density 1000 kg/m3) while suspended from a harness. Her apparent

weight is now 21.2 N. What is her density?

A) 1050 kg/m3

B) 1040 kg/m3

C) 1030 kg/m3

D) 960 kg/m3

E) 56.1 kg/m3

Answer: BVar: 1

19) A barge is 15.0 m wide and 75.0 m long and has vertical sides. The bottom of the hull is 1.20

m below the water surface. What is the weight of the barge and its cargo, if it is floating in fresh

water of density 1000 kg/m3?

A) 22.6 MN

B) 13.2 MN

C) 1.35 MN

D) 1.13 MN

E) 11.3 MN

Answer: BVar: 1

20) A hollow steel ball of diameter 3.0 m barely floats in water. What is the thickness of the wall

of the ball? The density of iron is 7.87 g/cm3 and that of water is 1000 kg/m3.

A) 6.6 cm

B) 37 cm

C) 131 cm

D) 79 cm

Answer: AVar: 1

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Wolfson Eup3 Ch15 Test Bank - baixardoc