Cutnell/Johnson Physics 9th edition

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Cutnell/JohnsonPhysics 9th edition

• Classroom Response System Questions

Chapter 11 Fluids
Interactive Lecture Questions
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• 11.1.1. Which one of the following objects has
  the largest mass?
• a) a gold solid cube with each side of length r
• b) a brass solid sphere of radius r
• a silver solid cylinder of height r and radius r
• a lead solid cube with each side of length r
• a concrete solid sphere of radius r

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11.1.2. Liquid A has a mass density of 850.0
kg/m3 and Liquid B has a mass density of 1060.0
kg/m3. Seventy-five grams of each liquid is
mixed uniformly. What is the specific gravity of
the mixture? a) 0.955 b) 0.943 c) 0.878 d)
0.651 e) 0.472
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11.1.3. What volume of helium has the same mass
as 5.0 m3 of nitrogen? a) 35 m3 b) 27 m3 c)
7.0 m3 d) 3.5 m3 e) 0.72 m3
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11.2.1. A swimmer is swimming underwater in a
large pool. The force on the back of the
swimmers hand is about one thousand newtons.
The swimmer doesnt notice this force. Why
not? a) This force is actually smaller than the
force exerted by the atmosphere. b) The force
is large, but the pressure on the back of the
hand is small. c) The force is exerted on all
sides equally. d) The swimmer is pushing on the
water with the same force. e) I do not know,
but Im sure I would feel that kind of force.
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11.2.2. In a classroom demonstration, a physics
professor lies on a bed of nails. The bed
consists of a large number of evenly spaced,
relatively sharp nails mounted in a board so that
the points extend vertically outward from the
board. While the professor is lying down, nearly
one thousand nails make contact with his body.
Which one of the following choices provides the
best explanation as to why the professor is not
harmed by the bed of nails? a) The nails are
not as sharp as nails typically used in
construction. b) The professor is wearing
special clothes that are not easily penetrated by
nails. c) The professors skin has been caliced
after years of doing the demonstration, so nails
no longer penetrate the skin. d) The
professors weight is distributed over all of the
nails in contact with the professors body, so
the pressure exerted a nail at any location is
too small to penetrate the skin. e) The force
due to gravity on the professor is balanced by
the upward force of the nails, as explained by
Newtons third law of motion, so the professor
doesnt accelerate downward.
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11.2.3. Amanda fills the two tires of her bicycle
to the pressure specified on the side wall of the
tires. She then gets onto her bicycle and
notices that the bottoms of the tires look
flatter than before she mounted the bicycle.
What happens to the pressure in the tires when
she is on the bicycle compared to when she was
off the bicycle? a) The pressure inside the
tire increases. b) The pressure inside the tire
decreases. c) The pressure inside the tire has
the same value.
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11.2.4. In snowy regions of the world, the local
people may wear snow shoes below their normal
shoes or boots. These snow shoes have a much
larger area than a regular shoe or boot. How
does a snow shoe improve a hikers ability to
walk across a snowy region? a) The hikers
weight is distributed over the area of the snow
shoes, which reduces the pressure on the snow
below and minimizes sinking into the snow. b)
The snow shoes increase the normal force of the
snow on the hiker. c) The snow shoes increase
the upward pressure of the snow on the hiker. d)
The snow shoes compact the snow making it harder
to sink into it. e) The hikers weight is
reduced by wearing large area snow shoes.
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11.2.5. Helium gas is confined within a chamber
that has a moveable piston. The mass of the
piston is 8.7 kg and its radius is 0.013 m. If
the system is in equilibrium, what is the
pressure exerted on the piston by the gas? a)
1.639 104 Pa b) 8.491 104 Pa c) 1.013
105 Pa d) 1.606 105 Pa e) 2.619 105 Pa
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11.2.6. Two balloons are connected via a pipe
with a closed valve as shown. One balloon has
five times the diameter of the other. Which of
the following will occur when the valve is
opened? a) Nothing will happen. Both
balloons will remain the same size. b) The
small balloon will get larger and the large one
will get smaller, but they will end up with
different sizes. c) The small balloon will get
larger and the large one will get smaller. They
will end up with equal sizes. d) Most of the
air in the smaller balloon will move into the
larger balloon. e) Most of the air in the
larger balloon will move into the smaller balloon.
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11.2.7. In which one of the following cases is
the pressure exerted on the ground by the man the
largest? a) A man stands with both feet flat on
the ground. b) A man stands with one foot flat
on the ground. c) A man lies with his back flat
on the ground. d) A man kneels with both knees
on the ground. e) A man stands with the toes of
one foot on the ground.
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11.2.8. Carol hangs a piece of stained glass
artwork that she has just completed on her window
using a suction cup hanger. Which one of the
following statements best explains the force that
holds the suction cup to the glass window? a)
There is a high amount of pressure between the
glass window and the suction cup. b) There is a
very low pressure between the glass window and
the suction cup. c) There is a smaller pressure
on the suction cup due to the atmosphere than the
pressure between the suction cup and the glass
window. d) There is a greater pressure on the
suction cup due to the atmosphere than the
pressure between the suction cup and the glass
window. e) Pushing the suction cup against the
glass window causes a very strong chemical bond
to form between the glass window and the suction
cup.
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11.2.9. What is the force that causes liquid to
move upward in a drinking straw as a person takes
a drink? a) that due to a low pressure region
caused by sucking b) that due to the pressure
within the liquid c) that due to atmospheric
pressure d) that due to the person sucking on
the straw e) that due to friction forces within
the straw
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11.3.1. You are vacationing in the Rocky
Mountains and decide to ride a ski lift to the
top of a mountain. As you go up, your feel your
ears make a pop sound because of changes in
atmospheric pressure. Which way does your ear
drum move, if at all, during your ascent up the
mountain? a) inward, because the pressure
outside the ear is larger than the pressure
inside the ear b) inward, because the pressure
outside the ear is smaller than the pressure
inside the ear c) No movement occurs. This is
just the sound of air bubbles bursting inside the
ear. d) outward, because the pressure outside
the ear is smaller than the pressure inside the
ear e) outward, because the pressure outside
the ear is larger than the pressure inside the ear
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11.3.2. Consider the mercury U-shaped tube
manometer shown. Which one of the following
choices is equal to the gauge pressure of the gas
enclosed in the spherical container? The
acceleration due to gravity is g and the density
of mercury is ?. a) ?gc b) ??gb c) ?ga d)
Patm ?gb e) Patm ? ?gc
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11.3.3. An above ground water pump is used to
extract water from a well. A pipe extends from
the pump to the bottom of the well. What is the
maximum depth from which water can be pumped? a)
19.6 m b) 39.2 m c) 10.3 m d) 101 m e)
With a big enough pump, you can extract it from
any depth.
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11.3.4. An aquarium has a length L, a width W,
and a height H. Glass of thickness d is used for
the sides of the aquarium. If you were to design
a similar aquarium, except that it has a length
5L and a width 5W, what thickness of glass would
you need to use? a) d b) c) 5d d)
10d e) 25d
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11.3.5. A water well is dug to a depth of 15
meters. A pump is used to bring the water upward
through a pipe, but the pump can only raise the
water about 7.5 meters. By which of the
following methods can the water be brought all
the way to the surface? a) Connect a second,
identical pump in series with the first pump. b)
Connect a second, identical pump in parallel
with the first pump. c) Replace the pump with a
more powerful pump. d) Replace the pipe with a
narrower pipe. e) None of these methods will
work.
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11.4.1. The height of mercury in one barometer is
0.761 m above the reservoir of mercury. If a
second barometer is brought to the same location
that has a liquid with a density of 2650 kg/m3,
what is the height of the fluid in the second
barometer? a) 0.761 m b) 2.02 m c) 2.87
m d) 5.03 m e) 3.91 m
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11.5.1. A fluid is completely enclosed in the
system shown. As the piston is moved to the
right, which one of the following statements is
true? (a) Pushing the piston to the right
causes the pressure on the left side of the
vertical cylinder to be larger than that on the
right side. (b) Pushing the piston to the right
causes the pressure on the bottom of the
vertical cylinder to be larger than that on the
top. (c) Pushing the piston to the right causes
the pressure throughout the vertical cylinder to
increase by the same amount. (d) Pushing the
piston to the right causes the pressure in one
part of the vertical cylinder and a corresponding
decrease in another part of the cylinder. (e)
After the piston is pushed by a distance s and
held in that position, the pressure will be the
same at all points within the fluid.
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11.5.2. At an automotive repair shop, a hydraulic
lift is used to raise vehicles so that mechanics
can work under them. In one lift, compressed air
with a maximum gauge pressure of 5.0 105 Pa is
used to raise a piston with a circular
cross-section and radius of 0.15 m. What is the
maximum vehicular weight that can be raised using
this lift? a) 7.5 104 N b) 6.0 104 N c)
4.4 104 N d) 3.5 104 N e) 1.1 104 N
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11.5.3. A woman stands on a platform with a
diameter D1 that acts as a piston. The combined
mass of the woman and the piston is 75 kg. The
piston pushes downward on a reservoir of oil that
supports a second platform with a diameter D2 on
which 12 women are standing. The combined mass
of the second platform and the 12 women is 780
kg. Both platforms are at the same height during
this demonstration and they are at rest. What
is the ratio D2/D1? a) 2.4 b) 3.2 c)
4.8 d) 10 e) 12
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11.6.1. A solid block of mass m is suspended in a
liquid by a thread. The density of the block is
greater than that of the liquid. Initially, the
fluid level is such that the block is at a depth
d and the tension in the thread is T. Then, the
fluid level is decreased such that the depth is
0.5d. What is the tension in the thread when the
block is at the new depth? a) 0.25T b)
0.50T c) T d) 2T e) 4T
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11.6.2. A fisherman rows his boat out to his
favorite spot on a pond, where he decides to drop
a heavy anchor from his boat. When he drops the
anchor into the pond, what happens to the level
of the pond? a) The level of the pond
decreases. b) The level of the pond stays the
same. c) The level of the pond increases.
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11.6.3. In the distant future, a base has been
constructed on the moon. Inside the base, a ball
is dropped into a container of water. Given that
the acceleration due to gravity is about one
sixth the value on the Earths surface, which of
the following statements correctly describes the
buoyant force on the ball? a) The buoyant force
is equal to 1/6 the weight of the displaced
water. b) The buoyant force is equal to 6 times
the weight of the displaced water. c) The
buoyant force is equal to the weight of the
displaced water. d) The buoyant force is equal
to 1/6 the weight of the ball. e) The buoyant
force is equal to the weight of the ball.
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11.6.4. A coin is dropped into a lake. As the
coin sinks, how does the buoyant force on the
coin change? a) The buoyant force decreases as
the depth increases. b) The buoyant force
increases as the depth increases. c) The
buoyant force decreases as the speed
increases. d) The buoyant force decreases as
the depth decreases. e) The buoyant force has a
constant value.
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11.6.5. Three fourths the volume of a glass is
filled with water. Ice is then added until it
reaches the top of the glass. The water level at
that point is h. Which one of the following
statements concerning the level of water after
the ice melts is true? a) The final level of
water will be lower than h. b) The final level
of water will be at h. c) The final level of
water will be higher than h. d) This cannot be
answered without knowing the mass of ice
added. e) This cannot be answered without
knowing the volume of ice added.
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11.6.6. A boy is playing in the bathtub with a
toy boat floating on the surface of the water.
His favorite rock is the cargo on the boat. If
the boy takes the rock from the boat and drops it
into the water, how will the water level of the
bathtub change, if at all? a) The water level
will rise. b) The water level will fall. c)
The water level will remain the same.
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11.8.1. At the site of a burning building, a
firefighter is using a hose with a radius of
0.032 m that has water flowing through it at a
rate of 0.032 m3/s. At the end of the hose,
there is a nozzle with a radius of 0.013 m.
First, calculate the speed of the water exiting
the nozzle and use that to determine the range,
the maximum horizontal distance the water can
reach, if it is directed at an angle of 45? with
respect to the horizon. a) 6.2 m b) 59 m c)
120 m d) 210 m e) 370 m
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11.8.2. A child has left an outdoor faucet open.
An adult walks up and notices that the diameter
of the stream is 0.25d at the bottom and d at the
top as it falls vertically from the faucet. What
is the physical explanation for this narrowing of
the stream? a) The flow rate at the top of the
stream is not sufficient to maintain a constant
cross-sectional area. b) Atmospheric pressure
is greater than the pressure within the stream of
water. c) The water has left the pipe that
carried it and no longer maintains the shape of
the pipe. d) The water accelerates as it falls
and the cross-sectional area must decrease to
maintain a constant flow rate. e) The stream of
water is experiencing friction with the air as it
falls and part of it slows down while part of it
falls at a constant speed.
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11.8.3. The drawing shows a section of a pipe
system in which an incompressible fluid can
either flow in or flow out various channels. All
of the pipes have the same diameter. The
direction and flow rates are indicated on the
drawing. What is the mass flow rate and
direction of flow for the unknown pipe? a) 0.2
m3/s b) 0.4 m3/s c) 0.6 m3/s d) 0.8
m3/s e) 1.0 m3/s
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11.9.1. Many tall buildings have reservoirs of
water on the roofs. The surface of these
reservoirs are at atmospheric pressure. If all
of the water in one tall building were delivered
from such a reservoir, would it be a good idea to
deliver water to all of the floors of the
building from a single pipe connected to the
reservoir? a) Yes, that would ensure a steady
flow of water at constant pressure on all
floors. b) Yes, that would ensure a steady flow
of water at a slightly varying pressure on all
floors. c) No, the pressure would be too large
on the lower floors and exit faucets at dangerous
speeds. d) No, the pressure would be too small
on the lower floors and would not exit faucets.
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11.9.2. A curtain hangs straight down in front of
an open window. A sudden gust of wind blows past
the window and the curtain is pulled out of the
window. Which law, principle, or equation can be
used to explain this movement of the curtain? a)
the equation of continuity b) Pascal's
principle c) Bernoulli's equation d)
Archimedes' principle e) Poiseuille's law
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11.9.3. Fluid is flowing from left to right
through the pipe shown in the drawing. Points A
and B are at the same height, but the
cross-sectional areas of the pipe are different
at the two locations. Points B and C are at two
different heights, but the cross-sectional areas
of the pipe are the same at these two locations.
Rank the pressures at the three locations in
order from lowest to highest? a) PA gt PB gt
PC b) PB gt PA PC c) PC gt PB gt PA d) PB gt
PA and PB gt PC e) PC gt PA and PC gt PB
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11.9.4. An air blower is attached to a funnel
that has a light-weight ball inside as shown.
How will the ball behave when the blower is
turned on? a) The ball will roll around inside
the funnel in random directions. b) The ball
will bounce around inside the funnel in random
directions. c) The ball will be drawn upward to
the top of the funnel and remain there. d) The
ball will remain stationary, unaffected by the
flowing air. e) The ball will spin rapidly as
it moves slowly around inside the funnel.
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11.9.5. A piece of paper is laying flat on a desk
near a closed window. When the window is opened,
air rushes over the top of the desk and the paper
is observed to be lifted upward and then carried
away by the wind. Which of the following
statements best describes why the paper was
lifted from the desk? a) The paper was
attracted by the force of the wind. b) The
pressure of the moving air above the paper was
greater than that of the air between the paper
and the desk top. c) The pressure of the moving
air above the paper was less than that of the air
between the paper and the desk top. d) The
weight of the paper was reduced by the wind
blowing over it and the normal force of the desk
was then greater than the weight. The normal
force pushes the paper upward. e) The wind
pushed the side of the paper and lifted it upward.