Conceptual Physical Science 5e – Chapter 5 © 2012 Pearson Education, Inc. Conceptual Physical Science 5 th Edition Chapter 5: Fluid Mechanics © 2012 Pearson

Conceptual Physical Science 5e – Chapter 5

© 2012 Pearson Education, Inc.

Conceptual PhysicalScience

5th Edition

Chapter 5:

FluidMechanics




Mercury has a density of 13.6 grams per cubic centimeter. How much heavier is it than one cubic centimeter of water?

A. 13.6 times heavier.

B. 1.0 times as heavy.

C. 37.2 times heavier.

D. None of these.



Mercury has a density of 13.6 grams per cubic centimeter. How much heavier is it than one cubic centimeter of water?

A. 13.6 times heavier.

B. 1.0 times as heavy.

C. 37.2 times heavier.

D. None of these.



At which hole in the cup is there more pressure on the water shooting out of the hole?

A. Hole 1.

B. Hole 2.

C. Hole 3.

D. Not enough information is given in this question.

Hole 1

Hole 2

Hole 3



At which hole in the cup is there more pressure on the water shooting out of the hole?

A. Hole 1.

B. Hole 2.

C. Hole 3.

D. Not enough information is given in this question.

Hole 1

Hole 2

Hole 3



Does a 3-meter-deep shallow lake or a 6-meter-deep small pond exert more pressure at the bottom of a dam that holds back the water?

A. The three-meter-deep shallow lake.

B. The six-meter-deep small pond.

C. Same amount of pressure is exerted (atmospheric) so same force.

D. Not enough information given in the question.



Does a 3-meter-deep shallow lake or a 6-meter-deep small pond exert more pressure at the bottom of a dam that holds back the water?

A. The three-meter-deep shallow lake.

B. The six-meter-deep small pond.

C. Same amount of pressure is exerted (atmospheric) so same force.

D. Not enough information given in the question.

Comment:

Deeper water, greater pressure!



There are three containers each with the same bottom surface area, A, and height, h. Which one contains the most mass of water?

A. 1

B. 2

C. 3

D. Equal mass of water.

h

A A A

1 2 3



There are three containers each with the same bottom surface area, A, and height, h. Which one contains the most mass of water?

A. 1

B. 2

C. 3

D. Equal mass of water.

Explanation:

Although the pressures at the bottom of each vessel are the same, clearly a greater mass of water occupies the wider vessel. If you got this wrong you likely didn’t answer the question asked. Read carefully!

h

A A A

1 2 3



Here are three containers, each with the same bottom surface area, A, and height of water, h. The container exerting the greatest pressure on the bottom surface is

A. 1

B. 2

C. 3

D. All at equal pressure.

h

A A A

1 2 3



Here are three containers, each with the same bottom surface area, A, and height of water, h. The container exerting the greatest pressure on the bottom surface is

A. 1

B. 2

C. 3

D. All at equal pressure.

h

A A A

1 2 3

Comment: The pressure at the bottom surface depends on the height of water above it, not its weight.



Consider two tubes filled with water at the same height, one with fresh water and the other with salt water. The pressure is greater at the bottom of the tube with

A. fresh water.

B. salt water.

C. both the same.

D. depends on whether the tubes have the same cross-sectional area.



Consider two tubes filled with water at the same height, one with fresh water and the other with salt water. The pressure is greater at the bottom of the tube with

A. fresh water.

B. salt water.

C. both the same.

D. depends on whether the tubes have the same cross-sectional area.



If a hole is punched in the side or bottom of a boat, water spurting in will be

A. perpendicular to the surface.

B. in an upward direction.

C. in such a way as to minimize flow rate.

D. conserved.



If a hole is punched in the side or bottom of a boat, water spurting in will be

A. perpendicular to the surface.

B. in an upward direction.

C. in such a way as to minimize flow rate.

D. conserved.



A fish normally displaces its own

A. weight of water.

B. volume of water.

C. Both of these.

D. Neither of these.



A fish normally displaces its own

A. weight of water.

B. volume of water.

C. Both of these.




A completely submerged object always displaces its

A. volume of fluid.

B. weight of fluid.

C. density of fluid.

D. All of these.



A completely submerged object always displaces its

A. volume of fluid.

B. weight of fluid.

C. density of fluid.

D. All of these.



What is the buoyant force acting on a 120-ton floating ship?

A. 120 tons in fresh water.

B. Slightly more than 120 tons in salt water.

C. Slightly less than 120 tons in salt water.

D. 120 tons in any water in which it floats.



What is the buoyant force acting on a 120-ton floating ship?

A. 120 tons in fresh water.

B. Slightly more than 120 tons in salt water.

C. Slightly less than 120 tons in salt water.

D. 120 tons in any water in which it floats.

Comment:

A ship will float higher in salt water, but will still displace its weight of water. Don’t confuse how high something floats with the buoyant force making it float.



When a submarine goes into a dive, it takes water into its ballast tanks, which makes the density of the submarine

A. less.

B. more.

C. unchanged.

D. None of these.



When a submarine goes into a dive, it takes water into its ballast tanks, which makes the density of the submarine

A. less.

B. more.

C. unchanged.

D. None of these.



Compared with the buoyant force that acts on a submarine floating at the surface, when submerged the buoyant force is

A. less.

B. more.

C. unchanged.

D. None of these.



Compared with the buoyant force that acts on a submarine floating at the surface, when submerged the buoyant force is

A. less.

B. more.

C. unchanged.

D. None of these.

Explanation:

Buoyant force is more because more water is being displaced. More buoyant force is acting on a heavier submarine.



When you float in salt water rather than in fresh water, the volume of water displaced is

A. less.

B. more.

C. unchanged.

D. None of these.



When you float in salt water rather than in fresh water, the volume of water displaced is

A. less.

B. more.

C. unchanged.

D. None of these.

Comment:

The smaller volume of denser water nevertheless gives a buoyant force equal to your weight. People can float slightly higher in salt water because they don’t have to displace as great a volume of water to equal their weight. (This may be a source of confusion with your classmates!)



A lobster crawls onto a bathroom scale submerged in water. Compared to its weight above water, its weight while submerged is

A. less.

B. the same.

C. more.

D. None of these.



A lobster crawls onto a bathroom scale submerged in water. Compared to its weight above water, its weight while submerged is

A. less.

B. the same.

C. more.

D. None of these.



Buoyant force is greatest on a submerged 1-cubic centimeter of

A. iron.

B. lead.

C. aluminum.

D. All the same.



Buoyant force is greatest on a submerged 1-cubic centimeter of

A. iron.

B. lead.

C. aluminum.

D. All the same.

Explanation:

All have the same size, so all displace the same volume and weight of water. Hence buoyant force is the same for each.



Buoyant force is greatest on a submerged 1-kg block of

A. iron.

B. lead.

C. aluminum.

D. All the same.



Buoyant force is greatest on a submerged 1-kg block of

A. iron.

B. lead.

C. aluminum.

D. All the same.

Explanation:

1 kg of aluminum is a bigger block and displaces more water!



Consider an air-filled balloon, weighted down so that it just barely is able to float on water. If you gently push it about a meter beneath the surface, after removing your hand the balloon will

A. come back to the surface.

B. sink.

C. stay at the level you push it to.

D. no longer be buoyant.



Consider an air-filled balloon, weighted down so that it just barely is able to float on water. If you gently push it about a meter beneath the surface, after removing your hand the balloon will

A. come back to the surface.

B. sink.

C. stay at the level you push it to.

D. no longer be buoyant.

Explanation:

Water pressure reduces balloon volume, increases density, so the balloon sinks. (This question is a “curve buster.”)



As a weighted air-filled balloon sinks in water, the buoyant force on the balloon

A. becomes less.

B. remains the same.

C. increases.

D. no longer acts at sufficient depth.



As a weighted air-filled balloon sinks in water, the buoyant force on the balloon

A. becomes less.

B. remains the same.

C. increases.

D. no longer acts at sufficient depth.

Explanation:

As the balloon sinks deeper, it’s squeezed by greater water pressure and its volume further decreases. Smaller volume displaces less water, so buoyant force decreases.



A boat filled with scrap iron floats in a swimming pool. If the scrap iron is thrown overboard into the pool, the water level at the side of the pool will

A. fall.

B. remain unchanged.

C. rise.

D. Actually, all of these!



A boat filled with scrap iron floats in a swimming pool. If the scrap iron is thrown overboard into the pool, the water level at the side of the pool will

A. fall.

B. remain unchanged.

C. rise.

D. Actually, all of these!

Explanation:

When the scrap iron is made to float (by being in the boat) it displaces its weight, which is considerable. But when submerged, it displaces only its volume, which displaces much less water than when the iron was made to float. So the water level falls!



When swimming, there’s a buoyant force on you. Is there a buoyant force on you when you’re not in the water?

A. No. If there was you would float in air.

B. Yes, a small amount due to displaced air.

C. Yes, which is why you’re sunk on the ground.

D. Yes, but only when there’s relative motion with the air.



When swimming, there’s a buoyant force on you. Is there a buoyant force on you when you’re not in the water?

A. No. If there was you would float in air.

B. Yes, a small amount due to displaced air.

C. Yes, which is why you’re sunk on the ground.

D. Yes, but only when there’s relative motion with the air.



When you squeeze an air-filled party balloon and reduce its volume, you increase its

A. density.

B. mass.

C. weight.

D. All of these.



When you squeeze an air-filled party balloon and reduce its volume, you increase its

A. density.

B. mass.

C. weight.

D. All of these.



The water-filled pair of caissons on the Falkirk Wheel have the same weight when both carry

A. equal-mass boats.

B. unequal-mass boats.

C. no boats, only water.

D. all of the above.



The water-filled pair of caissons on the Falkirk Wheel have the same weight when both carry

A. equal-mass boats.

B. unequal-mass boats.

C. no boats, only water.

D. all of the above.

Explanation:

Figure 5.16 says it all! Intriguing physics, indeed!



The famous “Magdeburg hemispheres” experiment of 1654 demonstrated atmospheric pressure. Two teams of horses couldn’t pull the evacuated hemispheres apart because the atmosphere

A. sucked them together.

B. pushed them together.

C. Neither of the above is correct.

D. Both of the above are correct.



The famous “Magdeburg hemispheres” experiment of 1654 demonstrated atmospheric pressure. Two teams of horses couldn’t pull the evacuated hemispheres apart because the atmosphere

A. sucked them together.

B. pushed them together.

C. Neither of the above is correct.

D. Both of the above are correct.



Two science types drink soda through a straw. They know this process works because atmospheric pressure

A. sucks the liquid upward.

B. pushes down on the liquid surface.

C. obeys Bernoulli’s principle.

D. is greater at the bottom of the drink.



Two science types drink soda through a straw. They know this process works because atmospheric pressure

A. sucks the liquid upward.

B. pushes down on the liquid surface.

C. obeys Bernoulli’s principle.

D. is greater at the bottom of the drink.



The water-filled U-tube with pistons at each end makes a hydraulic press. If the areas of the cylinders and pistons are the same, then a push downward on the left piston will produce in the right piston

A. the same amount of force.

B. the same amount of pressure.

C. Both of these.




The water-filled U-tube with pistons at each end makes a hydraulic press. If the areas of the cylinders and pistons are the same, then a push downward on the left piston will produce in the right piston

A. the same amount of force.

B. the same amount of pressure.

C. Both of these.




What will happen to the size of air bubbles in a narrowing pipe of moving water?

A. The air bubbles get smaller.

B. The air bubbles get bigger.

C. Some bubbles get bigger while others get smaller.

D. The air bubbles stay the same size.



What will happen to the size of air bubbles in a narrowing pipe of moving water?

A. The air bubbles get smaller.

B. The air bubbles get bigger.

C. Some bubbles get bigger while others get smaller.

D. The air bubbles stay the same size.



Pressure in air undergoes a decrease when the air

A. rises to higher altitudes.

B. accelerates to higher speed.

C. fills a greater space.

D. All of these.



Pressure in air undergoes a decrease when the air

A. rises to higher altitudes.

B. accelerates to higher speed.

C. fills a greater space.

D. All of these.

Comment:

In all three of these cases, air pressure drops.



Water from a fire hose knocks over a wooden shed. Compared with the pressure within the water, the pressure exerted against the shed is

A. less.

B. the same.

C. more.

D. nonexistent.



Water from a fire hose knocks over a wooden shed. Compared with the pressure within the water, the pressure exerted against the shed is

A. less.

B. the same.

C. more.

D. nonexistent.

Explanation:

Distinguish between the pressure in the water and the pressure water can exert on something that changes its momentum.



When water in a brook or a system of pipes flows from a wide region to a narrow region, the speed of water in the narrow region is

A. less.

B. about the same.

C. exactly the same.

D. more.



When water in a brook or a system of pipes flows from a wide region to a narrow region, the speed of water in the narrow region is

A. less.

B. about the same.

C. exactly the same.

D. more.

Comment:

This is in accord with the principle of continuity.



Two cans are placed apart on straws. When air is blown in-between the cans, what will they do?

A. Not move.

B. They will move away from each other.

C. They will move toward each other.

D. Not enough information in problem.



Two cans are placed apart on straws. When air is blown in-between the cans, what will they do?

A. Not move.

B. They will move away from each other.

C. They will move toward each other.

D. Not enough information in problem.



Airplane flight best illustrates

A. Pascal’s law.

B. Archimedes’ principle.

C. Bernoulli’s principle.

D. Boyle’s law.



Airplane flight best illustrates

A. Pascal’s law.

B. Archimedes’ principle.

C. Bernoulli’s principle.

D. Boyle’s law.

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Conceptual Physical Science 5e – Chapter 5 © 2012 Pearson Education, Inc. Conceptual Physical Science 5 th Edition Chapter 5: Fluid Mechanics © 2012 Pearson