Cutnell/Johnson Physics 8th edition

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Cutnell/JohnsonPhysics 8th edition

• Classroom Response System Questions

Chapter 6 Work and Energy
Reading Quiz Questions
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6.1.1. In which one of the following situations
is zero net work done? a) a bunch of bananas
are placed on a spring scale in the
supermarket b) a sky diver falls from an
airplane before opening her parachute c) a
horse pulls a wagon at a constant velocity d) a
snowball rolls down a hill e) a skateboarder
steps on a skateboard and begins to roll
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6.1.2. Work may be expressed using all of the
following units except a) watt b) joule c)
N ? m d) erg e) ft ? lb
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6.1.3. A 5.0-kg ball on the end of a chain is
whirled at a constant speed of 1.0 m/s in a
horizontal circle of radius 3.0 m. What is the
work done by the centripetal force during one
revolution? a) 2.5 J b) 1.7 J c) 1.2 J d)
0.56 J e) zero J
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6.1.4. Which one of the following is not a unit
of energy? a) joule b) watt c) newton ?
meter d) kilowatt ? hour e) foot ? pound
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6.1.5. Which one of the following combinations of
units is equal to the joule? a) kg ? m2/s b)
kg ? m c) kg ? m/s d) kg ? m2/s2 e) kg ? s
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6.1.6. In which one of the following
circumstances does the force do positive work on
the object? a) The direction of the force is
perpendicular to the objects displacement. b)
The direction of the force is in the opposite
direction to the objects displacement. c) No
matter the direction of the force, positive work
will be done if there is a displacement of the
object. d) The direction of the force is in
the same direction as the objects
displacement. e) The objects displacement is
zero meters as the force is applied.
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6.2.1. Which one of the following statements
concerning kinetic energy is true? a) The
kinetic energy of an object is directly
proportional to its speed. b) The kinetic
energy of an object is expressed in watts. c)
The kinetic energy of an object is a quantitative
measure of its inertia. d) The kinetic energy
of an object always has a positive value. e)
The kinetic energy of an object is always equal
to the objects potential energy.
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6.2.2. Which one of the following is an example
of an object with a non-zero kinetic energy? a)
A train is parked in a train station. b) A car
rests at the top of a hill. c) The pendulum of
a grandfather clock is still. d) A boulder
rests at the bottom of a cliff. e) The
International Space Station orbits the Earth.
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6.2.3. In which one of the following situations
will there be an increase in kinetic energy? a)
A kicked football approaches its maximum height
as it passes through the goal posts. b) The
planet Venus moves in its nearly circular orbit
around the Sun. c) A fan is switched from low
speed to high speed. d) A filing cabinet is
pushed across a rough floor at constant
speed. e) A train is pulled up a mountain at a
constant speed by a motor.
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6.2.4. Which one of the following expressions is
equal to the kinetic energy of an object? a)
mvt2 b) c) Fd cos ? d) ma e) mgh
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6.2.5. Complete the following statement If
positive work is done on a moving object, a)
the velocity of the object will increase. b)
the velocity of the object will decrease. c)
the kinetic energy of the object will
decrease. d) the velocity of the object will
not change. e) the direction of the
acceleration of the object will be opposite to
its displacement.
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6.3.1. In which one of the following systems is
there a decrease in gravitational potential
energy? a) A large boulder rests at the bottom
of a steep hill. b) A helicopter takes off from
the roof of a hospital and flies due west. c) A
child accidentally releases a helium-filled
balloon and it flies upward into the clouds. d)
A girl jumps down from a bed and lands on her
feet. e) A truck drives at an average velocity
of 25 m/s, due north along a level, country road.
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6.3.2. A man carries a 12-kg chair up one flight
of stairs to the second floor of his house. If
the second floor is 3.3 m above the first floor,
what is the change in the gravitational potential
energy of the chair? a) ?180 J b) 390 J c)
180 J d) ?390 J e) 240 J
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6.3.3. An arrow is launched straight up from the
surface of the Earth. Which one of the following
statements describes the energy transformation of
the arrow as it rises? Neglect air
resistance. a) The kinetic energy of the arrow
increases and its potential energy decreases. b)
Both the potential energy of the arrow and its
total energy increase. c) The kinetic energy of
the arrow decreases as the potential energy
increases. d) Both the kinetic energy of the
arrow and its potential energy remain
constant. e) The total energy of the arrow
increases.
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6.3.4. An object is initially at height y1.
After a time interval t, the object is located at
height y2. The work done by the gravitational
force on the object is dependent on which of the
following quantities? a) y1 ? y2 b) the path
taken from y1 to y2 c) the time interval t
taken to move from y1 to y2 d) choices a and
b e) choices a and c
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6.3.5. Alice and Bill, who happen to have the
same mass, both want to climb to the top of a
mountain. Bill wants to take the steep path
straight up, but Alice wants to take the path
that gently winds around the mountain, even
though it is 8 times longer than the steep path.
They both eventually reach the top of the
mountain, but Alice reaches the top in 1/3 the
time that Bill takes using the steep route. How
does the work that Alice did in climbing the
mountain compare with the amount that Bill
did? a) Alice did 1/8 the amount of work that
Bill did. b) Alice did 1/3 the amount of work
that Bill did. c) Alice and Bill did the same
amount of work. d) Alice did twice the amount
of work that Bill did. e) Alice did three times
the amount of work that Bill did.
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6.3.6. Sara carries a heavy box of books down a
flight of stairs from the third floor to the
first floor. Which one of the following
statements best describes the work done on the
box by Sara? a) Sara doesnt do any work on the
heavy box of books. b) Sara does a small amount
of negative work on the heavy box of books. c)
Sara does a small amount of positive work on the
heavy box of books. d) Sara does a large amount
of negative work on the heavy box of books. e)
Sara does a large amount of positive work on the
heavy box of books.
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6.3.7. What is the relationship between the
gravitational potential energy of an object and
the work done on the object by the gravitational
force? a) The work is equal to the
gravitational potential energy. b) The negative
of the work is equal to the change in the
gravitational potential energy. c) The negative
of the work is equal to the square of the
gravitational potential energy. d) The work is
equal to the square of the gravitational
potential energy. e) The work is equal to
one-half of the gravitational potential energy.
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6.4.1. Complete the following statement A force
that acts on an object is said to be conservative
if a) the work it does on the object is equal
to the increase in the object's kinetic
energy b) the work it does on the object is
independent of the path of the motion. c) it
always acts in the direction of motion of the
object. d) it results in a change in the
object's kinetic energy. e) it obeys Newton's
laws of motion.
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6.4.2. Which one of the following situations is
an example of a conservative force acting? a) A
boat motor produces a propulsion force that moves
the boat across a lake. b) The tension force in
the rope increased as the piano was lifted off
the ground. c) A child jumping on a trampoline
is pushed upward by an elastic spring force. d)
A normal force pushes upward on a book as it sits
on a table. e) The static frictional force
between the tires of a car and the road.
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6.4.3. Which one of the following choices is an
example of a non-conservative force? a) elastic
spring force b) gravitational force c)
kinetic frictional force d) electrical force
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6.4.5. Complete the following statement The net
work done by a conservative force acting on an
object a) depends only on the time that the
force is exerted. b) depends only on the
velocity of the object. c) depends only on the
starting and ending points. d) is always equal
to zero joules. e) is always greater than zero
joules.
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6.4.6. A ball is constrained to follow a circular
path by a conservative force. During a time
interval t, the ball makes exactly one
revolution. Which one of the following
statements concerning the net work done on the
ball during time t is true? a) The net work
depends only on the time t. b) The net work
depends only on the velocity of the ball. c)
The net work depends only on the radius of the
circle. d) The net work is equal to zero
joules. e) The net work is greater than zero
joules.
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6.5.1. Which one of the following statements
concerning the principle of the conservation of
mechanical energy is true? a) Mechanical energy
is always conserved in situations where the
kinetic energy is constant. b) Mechanical
energy is always conserved in situations where
the gravitational potential energy is
constant. c) Mechanical energy is always
conserved in situations where external
non-conservative forces do no work. d)
Mechanical energy is always conserved in
situations where external conservative forces do
no work. e) Mechanical energy is always
conserved in situations where the gravitational
potential energy is zero joules.
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6.5.2. Complete the following statement In an
isolated system, the total mechanical energy
remains constant if a) all exerted forces are
conservative. b) all exerted forces are
nonconservative. c) the work done by
nonconservative forces is positive. d) the work
done by nonconservative forces is negative. e)
an object returns to its starting position.
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6.5.3. Complete the following statement The
total mechanical energy of a system remains
unchanged if a) the external forces acting on
the system are nonconservative. b) the external
forces acting on the system are conservative. c)
the kinetic energy is constant. d) the
potential energy is constant. e) there are no
external forces acting on the system.
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6.5.4. A ball is thrown vertically upward in the
air. Which one of the following quantities is
necessarily equal to zero at the highest point of
the balls trajectory? a) acceleration b) net
force c) potential energy d) kinetic
energy e) total mechanical energy
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6.6.1. Complete the following statement In
situations involving non-conservative external
forces, the work done by these forces a) is
always negative. b) is always equal to
zero. c) is always positive. d) can be either
positive or negative. e) usually cannot be
determined.
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6.7.1. Power may be expressed using all of the
following units except a) watt b)
joules/second c) N ? m ? s d) erg/s e) ft ?
lb / h
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6.7.2. The power due to a force depends on which
of the following parameters? a) the magnitude
of the force and the displacement of the
object b) the magnitude of the force and the
velocity of the object c) the mass of the
object and the velocity of the object d) the
work done on the object and its displacement e)
the mass of the object and the displacement of
the object
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6.8.1. Which one of the following statements
concerning the principle of conservation of
energy is false? a) The total energy in the
universe has a constant value. b) Kinetic
energy may be converted into gravitational
potential energy and heat. c) Thermal energy
may be converted into kinetic energy and kinetic
energy may be converted into thermal energy. d)
Chemical energy may be converted into thermal
energy and gravitational potential energy. e)
The net work done on an object must be zero
joules since energy is neither created nor
destroyed in the process.