Deck 7: Fluid Mechanics

Question 1

A rock suspended by a string weighs 5 N out of water and 3 N when submerged. What is the buoyant force on the rock?

A) 3 N
B) 5 N
C) 2 N
D) 8 N
E) none of these

Answer 1

2 N

Question 2

The density of a submerged submarine is about the same as the density of

A) water.
B) iron.
C) a floating submarine.
D) a crab.
E) none of these

Answer 2

water.

Question 3

When holes are drilled through the wall of a water tower , water will spurt out the greatest horizontal distance from the hole closest to

A) the middle of the tower.
B) the top of the tower.
C) the bottom of the tower.
D) The horizontal distance will be the same for all holes.

Answer 3

the bottom of the tower.

Question 4

When an ice cube in a glass of water melts, the water level

A) falls.
B) rises.
C) remains the same.

Question 5

A one-ton blimp hovers in the air. The buoyant force acting on it is

A) zero.
B) more than one ton.
C) one ton.
D) less than one ton.

Question 6

A scale from which a rock is suspended reads 5 N when the rock is out of water and 3 N when the rock is submerged. The density of the rock is

A) 1.5 times the density of water.
B) the density of water.
C) 3.5 times the density of water.
D) 2.5 times the density of water.

Question 7

A swimmer cannot use a long hose to snorkel more than a meter deep because air

A) in the lungs cannot easily be expelled.
B) is buoyed up leaving the swimmer breathless.
C) tends to liquify in the snorkel tube.
D) at the surface will not freely enter the higher-pressure region in the compressed lungs.
E) all of these

Question 8

The mass of a cubic meter of water is

A) 100 kg.
B) 1000 kg.
C) 1 kg.
D) 10 kg.
E) 9800 N.

Question 9

Compared to the buoyant force of the atmosphere on a 1-liter helium-filled balloon, the buoyant force of the atmosphere on a nearby 1-liter solid iron block is

A) the same.
B) considerably less.
C) considerably more.

Question 10

A suction cup sticks to a wall. It is

A) pulled to the wall by the vacuum.
B) pushed to the wall by the atmosphere.
C) both of these
D) neither of these

Question 11

A balloon is buoyed up with a force equal to the

A) atmospheric pressure.
B) weight of the balloon and contents.
C) weight of air it displaces.
D) density of surrounding air.
E) all of these

Question 12

Three icebergs are each floating in bathtubs filled to the brim with water. Iceberg A has large air bubbles in it. Iceberg B has unfrozen water in it. Iceberg C has an iron railroad spike in it. When the ice melts, what happens?

A) The water level in C will decrease while the other two water levels will remain the same.
B) The water level in A will stay the same, while the other tubs will spill over.
C) Only the water in C will spill over.
D) All the tubs spill over.
E) All stay exactly the same.

Question 13

The pressure in a liquid depends on liquid

A) depth.
B) density.
C) both of these
D) neither of these

Question 14

A heavy glass ball is placed in a pie pan that floats in a bucket. The water level at the side of the bucket is marked. Then the glass ball is removed and allowed to sink in the bucket. The water line at the side of the bucket is now

A) lower.
B) higher.
C) the same.

Question 15

A hydraulic press multiplies a force by 100. This multiplication is done at the expense of

A) the distance through which the force acts.
B) energy, which is divided by 100.
C) the mechanism providing the force.
D) the time through which the force acts, which is multiplied by 100.
E) none of these

Question 16

The pressure at the bottom of a jug filled with water does NOT depend on

A) the acceleration due to gravity.
B) surface area of the water.
C) the height of the liquid.
D) water density.
E) none of these

Question 17

If a strong wind from the west breaks a window in the north wall of a house, most of the glass will fall

A) inside the house.
B) outside the house.
C) upward.

Question 18

Buoyant force is greatest on a submerged

A) 1-kg block of lead.
B) 1-kg block of aluminum.
C) is the same on each

Question 19

The buoyant force on a rock is least when the rock is submerged

A) near the bottom.
B) near the surface.
C) halfway to the bottom.
D) all of the above

Question 20

Gas pressure inside an inflated stretched balloon is actually

A) greater than air pressure outside the balloon.
B) less than air pressure outside the balloon.
C) equal to air pressure outside the balloon.
D) impossible to determine without knowing the type of gas.

Question 21

As a balloon rises higher and higher into the atmosphere, its

A) weight increases.
B) density increases.
C) mass decreases.
D) volume decreases.
E) none of these

Question 22

In a hydraulic-press operation, it is impossible for the

A) force output to exceed the force input.
B) energy output to exceed the energy input.
C) output displacement to exceed the input displacement.
D) output piston's speed to exceed the input piston's speed.
E) none of these

Question 23

When water is turned on in a shower, the shower curtain moves towards the water. This has to do with

A) heat capacity.
B) capillary action.
C) surface tension.
D) pressure of a moving fluid.
E) none of these

Question 24

The reason a life jacket helps you float is

A) if you sink, the jacket sinks.
B) the jacket has the same density as an average human.
C) the jacket repels water.
D) the jacket makes you weigh less.
E) the density of both you and the jacket together is less than your density alone.

Question 25

The Bernoulli effect causes passing ships to be drawn together when the ships are close and moving in

A) opposite directions.
B) the same direction.
C) either the same or opposite directions.

Question 26

A helium-filled balloon released in the atmosphere will rise until

A) atmospheric pressure on the bottom of the balloon equals atmospheric pressure on the top of the balloon.
B) the pressure inside the balloon equals atmospheric pressure.
C) the balloon and surrounding air have equal densities.
D) all of these
E) none of these

Question 27

A lobster crawls onto a bathroom scale submerged at the bottom of the ocean. Compared to its weight above the surface, the lobster will have an apparent weight under water that is

A) greater.
B) less.
C) the same.

Question 28

The buoyant force on an object is least when the object is

A) submerged near the surface.
B) partly submerged.
C) submerged near the bottom.
D) none of these

Question 29

About what percentage of the molecules that make up the atmosphere are below an aircraft that flies at an altitude of 6 kilometers?

A) 30%
B) 40%
C) 50%
D) 20%
E) more than 50%

Question 30

The weight of a 1-square-meter column of air that extends from sea level to the top of the atmosphere is

A) 101 N.
B) 10,100 N.
C) 101,000,000 N.
D) 101,000 N.

Question 31

An ice cube floating in a glass of water contains many air bubbles. When the ice melts, the water level will

A) rise.
B) fall.
C) remain unchanged.

Question 32

To multiply the input force of a hydraulic lift, the input end should be the one having the

A) smaller diameter piston.
B) relative piston sizes don't matter.
C) larger diameter piston.

Question 33

A liter-sized block of ordinary wood floats in water. The amount of water displaced is

A) 1 liter.
B) less than 1 liter.
C) more than 1 liter.
D) depends on the water density
E) none of these

Question 34

When an object is partly or wholly immersed in a liquid, it is buoyed up

A) by a force equal to the weight of liquid displaced.
B) but nevertheless sinks.
C) by a force equal to its own weight.
D) and floats because of Archimedes principle.
E) none of these

Question 35

An umbrella tends to move upwards on a windy day principally because

A) air gets trapped under the umbrella, warms, and rises.
B) air pressure is reduced over the curved top surface.
C) buoyancy increases with increasing wind speed.
D) all of these

Question 36

The ratio of output force to input force of a hydraulic press will be equal to the ratio of the output and input piston

A) areas.
B) diameters.
C) radii.
D) all of these
E) none of these

Question 37

A boat loaded with wood floats in a swimming pool. When the wood is thrown overboard, the pool level will

A) fall.
B) rise.
C) remain unchanged.

Question 38

A boat loaded with scrap iron floats in a swimming pool. When the iron is thrown overboard, the pool level will

A) fall.
B) rise.
C) remain unchanged.

Question 39

A block of wood with a piece of iron tied to the top of it floats in a bucket of water. If the wood and iron are turned over so that the iron is submerged beneath the wood, the water level at the side of
The bucket

A) falls.
B) rises.
C) remains the same.

Question 40

Blood pressure is normally greater in your

A) feet.
B) ears.
C) same in each

Question 41

Two life preservers have identical volumes, but one is filled with styrofoam while the other is filled with sand. When the two life preservers are worn by swimmers so that one swimmer floats with part of the preserver above water, and the other swimmer sinks, the buoyant force is actually greater on the life preserver filled with

A) sand.
B) styrofoam.
C) same

Question 42

Airplane flight best illustrates

A) Bernoulli's principle.
B) Boyle's law.
C) Pascal's principle.
D) Archimedes' principle.

Question 43

Buoyant force is greatest on a submerged

A) 10-newton block of aluminum.
B) 10-newton block of lead.
C) is the same on each

Question 44

As a high-altitude balloon sinks lower and lower into the atmosphere, it undergoes a decrease in

A) density.
B) volume.
C) mass.
D) weight.
E) none of these

Question 45

Atmospheric pressure is caused by the

A) temperature of the atmosphere.
B) density of the atmosphere.
C) effect of the sun's energy on the atmosphere.
D) weight of the atmosphere.

Question 46

Ice cubes submerged at the bottom of a liquid indicate that the liquid

A) is warmer than the ice.
B) produces no buoyant force on the ice.
C) is less dense than ice.
D) has dissolved air.
E) is not displaced by the submerged ice.

Question 47

The reason that buoyant force acts upward on a submerged object is that

A) if it acted downward, nothing would float.
B) the weight of fluid displaced reacts with an upward force.
C) upward pressure against the bottom is greater than downward pressure against the top of the submerged object.
D) it acts in a direction to oppose gravity.

Question 48

Two life preservers have identical volumes, but one is filled with styrofoam while the other is filled with sand. When the two life preservers are fully submerged, the buoyant force is greater on the
One filled with

A) sand.
B) styrofoam.
C) same on each as long as their volumes are the same

Question 49

Water pressure is greatest against the

A) sides of a submerged object.
B) top of a submerged object.
C) bottom of a submerged object.
D) is the same against all surfaces
E) none of these

Question 50

Compared to the buoyant force of the atmosphere on a 1-kilogram helium-filled balloon, the buoyant force of the atmosphere on a nearby 1-kilogram solid iron block is

A) considerably more.
B) considerably less.
C) the same.

Question 51

A fish normally displaces its own

A) weight of water.
B) volume of water.
C) both of these
D) neither of these

Question 52

Two equal sized buckets are filled to the top with water. One of the buckets has a piece of wood floating in it, making its total weight

A) more than the weight of the other bucket.
B) less than the weight of the other bucket.
C) equal to the weight of the other bucket.

Question 53

Lobsters live on the bottom of the ocean. The density of a lobster is

A) less than the density of sea water.
B) greater than the density of sea water.
C) equal to the density of sea water.

Question 54

Wind blowing over the top of a hill

A) increases atmospheric pressure there.
B) decreases atmospheric pressure there.
C) does not affect atmospheric pressure there.

Question 55

If a battleship sinks in a canal lock, the water level in the lock will

A) fall.
B) rise.
C) remain unchanged.

Question 56

A dam is thicker at the bottom than at the top partly because

A) surface tension exists only on the surface of liquids.
B) water is denser at deeper levels.
C) it looks better.
D) water pressure is greater with increasing depth.
E) none of these

Question 57

On a windy day, atmospheric pressure

A) remains unchanged.
B) decreases.
C) increases.

Question 58

When gas in a container is squeezed to half its volume and the temperature remains the same, the gas pressure

A) doubles.
B) remains the same.
C) quadruples.
D) halves.

Question 59

The flight of a blimp best illustrates

A) Bernoulli's principle.
B) the principle of Archimedes.
C) Pascal's principle.
D) Boyle's law.

Question 60

A common 5-liter metal can will float in air if it is

A) thrown high enough into the air.
B) evacuated of air.
C) filled with a very large amount of helium.
D) Nonsense! Unless the displaced air weighs more than the can and its contents, the can will not float in air.

Question 61

A row boat containing a barrel of water floats in a swimming pool. When the water in the barrel is poured overboard, the swimming pool level will

A) fall.
B) rise.
C) remain unchanged.

Question 62

Compared to an empty ship, the same ship loaded with styrofoam will float

A) higher in the water.
B) at the same level in the water.
C) lower in the water.

Question 63

Buoyant force is greatest on a submerged

A) 1-cubic centimeter block of aluminum.
B) 1-cubic centimeter block of lead.
C) is the same on each

Question 64

The volume of water displaced by a floating 20-ton boat

A) depends on the shape of the ship's hull.
B) is the volume of the boat.
C) is the volume of 20 tons of water.
D) is 20 cubic meters.
E) none of these

Question 65

When a boat sails from fresh water to salt water, the boat will float

A) lower in the water.
B) higher in the water.
C) at the same water level.

Question 66

What is the approximate mass of a 1-square-centimeter column of air that extends from sea level to the top of the atmosphere?

A) 100 kilograms
B) 1 kilogram
C) 1 gram
D) 10 kilograms

Question 67

The depth to which an inverted drinking glass must be pushed beneath the surface of water so that the volume of enclosed air is squeezed to half is

A) 76 cm.
B) 29.4 m.
C) 10.3 m.
D) 20.6 m.
E) 14.7 m.

Question 68

A completely submerged object always displaces its own

A) weight of fluid.
B) density of fluid.
C) volume of fluid.
D) all of these
E) none of these

Question 69

If the part of an iceberg that extends above the water were suddenly removed, the

A) buoyant force on the iceberg would decrease.
B) pressure on the bottom of the iceberg would increase.
C) iceberg would sink.
D) density of the iceberg would change.
E) none of these

Question 70

A block of styrofoam floats on water while a same size block of lead lies submerged in the water. The buoyant force is greatest on the

A) styrofoam.
B) lead.
C) is the same for both

Question 71

What is the weight of water displaced by a 100-ton floating ship?

A) more than 100 tons
B) 100 cubic meters
C) 100 tons
D) less than 100 tons
E) depends on the ship's shape

Question 72

A bubble of air released from the bottom of a lake

A) alternately expands and contracts as it rises.
B) becomes larger as it rises.
C) rises to the top at constant volume.
D) becomes smaller as it rises.
E) none of these

Question 73

As a helium-filled balloon rises in the air, it becomes

A) heavier.
B) more dense.
C) bigger.
D) all of these
E) none of these

Question 74

A floating ice cube contains small pieces of iron. During melting the water level will

A) fall.
B) rise.
C) remain unchanged.

Question 75

An egg is placed at the bottom of a bowl filled with water. Salt is slowly added to the water until the egg rises and floats. From this experiment, one concludes

A) salt sinks to the bottom.
B) the density of salt water exceeds the density of egg.
C) buoyant force does not always act upward.
D) calcium in the egg shell is repelled by sodium chloride.

Question 76

When gas in a container is squeezed to half its volume, its density

A) quadruples.
B) halves.
C) doubles.
D) remains the same.

Question 77

About how high can water be theoretically lifted by a vacuum pump at sea level?

A) more than 10.3 m
B) 10.3 m
C) less than 10.3 m

Question 78

A block of wood half as dense as water floats with half its volume above water. A piece of iron is then tied on top so the wood floats with only 1/4 its volume above the surface. If the wood and iron
Are turned over so that the iron is submerged beneath the wood, then the volume of wood above the water surface will be

A) the same, 1/4.
B) more than 1/4.
C) less than 1/4.
D) There's no way to say.

Question 79

Pumice is a volcanic rock that floats. Its density is

A) equal to the density of water.
B) less than the density of water.
C) more than the density of water.

Question 80

Compared to the density of water, the density of a fish is

A) less.
B) more.
C) the same.