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Cutnell/Johnson
Physics 8th edition
Classroom Response System Questions
Chapter 7 Impulse and Momentum
Reading Quiz Questions
7.1.1. Which one of the following statements is true concerning
momentum?
a) Momentum is a force.
b) Momentum is a velocity.
c) Momentum is a scalar quantity.
d) The momentum of an object is always positive.
e) Momentum and impulse are measured in the same units.
7.1.2. As the name implies, the impulse-momentum theorem provides a relationship
between impulse and momentum. Which one of the following statements
correctly describes that relationship?
a) An impulse is equal to the work done on an object when a net force acts on an
object and it has a displacement.
b) An impulse is equal to the change in an object’s momentum that occurs when a
net force acts on it.
c) An impulse is equal to one-half of the object’s momentum squared.
d) An impulse is equal to the product of the net force acting on the object and its
momentum.
e) An impulse is equal to the object’s momentum divided by the product of the net
force and the time interval during which the force acts.
7.1.3. Momentum may be expressed using which of the following
units?
a) N/s
b) kg/m
c) kg  m/s
d) kg/(m  s)
e) N  kg/s
7.1.4. The momentum of an object is not dependent on which one of
the following quantities?
a) acceleration
b) inertia
c) mass
d) speed
e) velocity
7.1.5. Complete the following statement: The change in momentum
with respect to time for an object
a) is always positive.
b) is always equal to zero.
c) has a constant value if the force acting on the object is
conservative.
d) is equal in magnitude to the net force acting on the object, but
opposite in direction.
e) is a scalar quantity that may be negative, zero, or positive.
7.1.6. Which one of the following statements concerning the
momentum of a system when the net force acting on the system
has a positive value is true?
a) The momentum of the system is increasing.
b) The momentum of the system is decreasing.
c) The momentum of the system is equal to zero kg  m/s.
d) The momentum of the system has a constant value.
e) The momentum of the system has a negative value.
7.1.7. Which one of the following statements is true concerning
momentum?
a) Momentum is a force.
b) Momentum is a velocity.
c) Momentum is a scalar quantity.
d) The momentum of an object is always positive.
e) Momentum is measured in kg  m/s.
7.1.8. Which of the following units are used for an impulse?
a) kg  m/s
b) kg / m
c) N / s
d) kg / (m  s)
e) N  kg / s
7.1.9. Which one of the following quantities is equal to the change in
momentum of an object during a collision?
a) impulse
b) net force
c) work
d) change in kinetic energy
e) maximum force
7.2.1. In which one of the following situations is linear momentum not
conserved?
a) A golf ball is struck by a putter.
b) A bowling ball collides with ten pins.
c) A tree limb is struck by lightning and falls to the ground.
d) A bomb suspended by a string explodes into one hundred
fragments.
e) An astronaut floating in space throws a hammer away and
subsequently moves in the opposite direction.
7.2.2. A rocket is propelled forward as very high speed gases are ejected out
of its back. Which one of the following is the best explanation as to why
the rocket is propelled forward?
a) The rocket is propelled forward due to the conservation of energy.
b) The rocket is propelled forward due to the conservation of momentum.
c) Because the gases are pushing against the air, the air propels the rocket
forward.
d) The rocket is propelled forward because both energy and momentum
must be conserved.
e) The high speed gases push on the rocket as they are ejected and propel it
forward.
7.2.3. During a certain process, the linear momentum of a system is
conserved. Which one of the following statements concerning this
system is correct?
a) The vector sum of the momentum of the objects that make up the system
is equal to zero kg  m/s.
b) The vector sum of any internal forces within the system results in an
acceleration of one or more objects within the system.
c) The principle of the conservation of mechanical energy automatically
applies to the system.
d) The vector sum of the average external forces acting on the system is
equal to zero newtons.
e) No internal or external forces are acting on the objects within the system.
7.2.4. A rifle of mass M is initially at rest. A bullet of mass m is fired
from the rifle with a velocity v relative to the ground. Which one
of the following expressions gives the velocity of the rifle relative
to the ground after the bullet is fired.
a) mv
b) mv
c) Mv/m
d) mv/M
e) mv/M
7.2.5. Which one of the following statements concerning the
momentum of a system when the net force acting on the system is
equal to zero newtons is true?
a) The momentum of the system is increasing.
b) The momentum of the system is decreasing.
c) The momentum of the system is equal to zero kgm/s.
d) The momentum of the system has a constant value.
e) The momentum of the system has a negative value.
7.3.1. A collision between two objects is elastic. Which one of the
following statements concerning this situation is true?
a) The total kinetic energy of the objects is the same before and after the
collision.
b) The total momentum of the objects is zero kgm/s after the collision.
c) The objects stick together and move as one object after the collision.
d) The kinetic energy of the objects is zero joules after the collision.
e) The vector sum of the velocities of the two objects is equal to zero m/s
after the collision.
7.3.2. Which one of the following provides a basis to distinguish
different types of collisions?
a) conservation of linear momentum
b) conservation of mechanical energy
c) conservation of kinetic energy
d) conservation of impulse
e) conservation of mass
7.3.3. A collision between two objects is inelastic. Which one of the
following statements concerning this situation is true?
a) The vector sum of the velocities of the two objects is equal to zero
m/s after the collision.
b) The total momentum of the objects after the collision is less than it
was before the collision.
c) The objects bounce away from each other after the collision.
d) The kinetic energy of the objects is zero joules after the collision.
e) The total kinetic energy of the objects after the collision is less than
it was before the collision.
7.3.4. A boy of mass m runs with a speed v and jumps onto a sled on
an icy pond. The sled was at rest before the boy jumped onto it.
After the jump, the sled and boy move at a speed v/2. What is the
mass of the sled?
a) m/2
b) m
c) 2m
d) 3m
e) 4m
7.3.5. Two objects are involved in an elastic collision. Which one of
the following statements concerning this situation is false?
a) The total momentum is conserved.
b) The magnitude of the force exerted by each object on the other
object is equal.
c) The kinetic energy of each object is the same before and after the
collision.
d) The total kinetic energy before the collision is equal to the total
kinetic energy after the collision.
e) The total kinetic energy is conserved.
7.3.6. During a maneuver in space, a space craft separates into two
pieces, each of mass m. Before the separation, the spacecraft was
moving with a speed v. If one of the pieces is at rest after the
separation, which one of the following statements concerning this
maneuver is true?
a) This maneuver conserves kinetic energy.
b) The maneuver does not conserve total energy.
c) This maneuver does not conserve momentum.
d) If one piece is at rest, the other is moving with a speed 2v.
e) One piece cannot be at rest. The must both be moving with a speed
v/2.
7.3.7. Which one of the following quantities is conserved during an
elastic collision, but not conserved during an inelastic collision?
a) momentum
b) kinetic energy
c) total energy
d) impulse
e) net force
7.4.1. Two pucks on an air hockey table collide elastically. Complete the
following statement: when such a collision occurs in two dimensions,
the before and after velocities are best determined by
a) using the fact that momentum is conserved and that the initial speeds
of the objects must equal the final speeds of the objects.
b) remembering that momentum is a vector quantity that is conserved in
each direction.
c) applying Newton’s second law of motion and setting the net force
equal to zero newtons.
d) making use of the work-energy theorem.
e) using the fact that the total energy is conserved.
7.5.1. Which one of the following statements concerning the center of
mass of an object is true?
a) The velocity of the center of mass of a system of objects is constant
when the sum of the external forces acting on the system is zero.
b) The center of mass of a system of objects cannot change even if
there are forces acting on the objects.
c) All of an object’s mass is located at its center of mass.
d) The velocity of the center of mass of a system of objects is greatly
affected by a collision of objects within the system.
e) The center of mass of an object must be located within the object.
7.5.2. Complete the following statement: The center of mass is
a) the region of an object where the density has the largest value.
b) the region of an object where most of the mass is located.
c) the point within an object that moves as if all of the object’s mass
where located there.
d) the point at the geometrical center of an object.
e) the only point on an object at which the gravitational force acts.
7.5.3. Three objects are located in the x-y plane as shown in the figure.
Determine the x coordinate of the center of mass for this system of
three objects. Note the masses of the objects: mA = 6.0 kg, mB =
2.0 kg, and mC = 4.0 kg.
a) 5.6
b) 6.3
c) 7.6
d) 8.3
e) 8.9
7.5.4. Complete the following statement: the center of mass of a
system of particles has a constant velocity if
a) the velocity of the center of mass is initially zero
b) the particles are distributed symmetrically around the center of
mass
c) the forces exerted by the particles on each other sum to zero
d) the center of mass is at the geometric center of the system
e) the external forces acting on particles of the system sum to zero
7.5.5. Bird A, with a mass of 2.2 kg, is stationary while Bird B, with a
mass of 1.7 kg, is moving due north from Bird A at 3 m/s. What is
the velocity of the center of mass for this system of two birds?
a) 1.4 m/s, due north
b) 0.77 m/s, due north
c) 1.7 m/s, due north
d) 0.77 m/s, due south
e) 1.4 m/s, due south