True/False
Indicate whether the
sentence or statement is true or false.
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1. |
The
impulse you give to a child on a swing to start the child moving is
equal in magnitude, but opposite in direction, to the child’s change
in momentum.
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2. |
Newton’s second law of motion can be written both as 
and 
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3. |
If
you have developed your follow-through skills when playing tennis, you
have increased the force you are able to apply as you swing the racket.
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For
questions 4 to 6, refer to Figure 1 .
Figure 1
In
this isolated system, two gliders (m1 = m2)
on an air track move toward each other at equal speed, collide, and
then move away from each other at equal speed.
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4. |
The
total momentum before the collision is positive, and the total momentum
after the collision is negative.
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5. |
For
this collision, if the change in momentum of glider 1 is -1.4 kg×m/s [W], then the change in momentum of glider
2 is 1.4 kg×m/s
[W].
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6. |
At
the exact midpoint of the collision, both the kinetic energy and the
momentum of the system are zero.
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7. |
If
a small car of mass mS and speed vS
has a momentum equal in magnitude to a large car of mass mB
and speed vB, then the two cars have equal kinetic
energies.
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8. |
When
a snowball hits a tree and sticks entirely to the tree, the momentum
of the snowball is not conserved because the collision is completely
inelastic.
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9. |
Elastic collisions are more likely to occur between atoms and molecules
than between macroscopic objects.
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10. |
In
an interaction involving an isolated system, it is impossible for the
final kinetic energy to be greater than the initial kinetic energy.
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Multiple Choice
Identify
the letter of the choice that best completes the statement or answers
the question.
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11. |
Using
L, M, and T for the dimensions of length, mass, and time,
respectively , the dimensions of impulse are
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12. |
If
an arrow’s speed and mass are both doubled, then its momentum and
kinetic energy are respectively increased by factors of
a. |
2 and 2 |
b. |
2 and 4 |
c. |
4 and 4 |
d. |
4 and 8 |
e. |
8 and 8 |
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13. |
The
area under the line on a force-time graph indicates
a. |
the impulse |
b. |
the change in momentum |
c. |
the
product of the average force and the time interval during which
that force is applied |
d. |
all
of these |
e. |
none of these |
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14. |
When
you catch a fast-moving baseball, your hand hurts less if you move it
in the same direction as the ball because
a. |
the
change in momentum in the ball is less |
b. |
the change in kinetic energy of the ball is less |
c. |
the
time interval of the interaction is less |
d. |
the time interval of the interaction is greater |
e. |
the impulse on the ball is greater |
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15. |
The
force applied by an apple hitting the ground depends on
a. |
whether or not the apple bounces |
b. |
the
time interval of the impact with the ground |
c. |
the apple’s maximum speed just before impact |
d. |
the air resistance acting on the apple as it falls |
e. |
all of these |
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16. |
In
an inelastic collision involving two interacting objects, the final
kinetic energy of the system
a. |
can
be equal to the initial kinetic energy of the system |
b. |
is always less than or equal to the initial kinetic
energy of the system |
c. |
is always greater than or equal to the initial
kinetic energy of the system |
d. |
is always less than the initial kinetic energy
of the system |
e. |
can be greater than the initial kinetic energy
of the system |
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17. |
When
you are jogging and you increase your kinetic energy by a factor of
2, then your momentum
a. |
changes
by a factor of  |
b. |
increases
by a factor of  |
c. |
increases
by a factor of 2 |
d. |
increases
by a factor of 4 |
e. |
increases
by an amount that cannot be determined with the information given |
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18. |
A
rubber bullet R and a metal bullet M of equal mass strike a test target
T with the same speed. The metal bullet penetrates the target and comes
to rest inside it, while the rubber bullet bounces off the target. Which
statement is true?
a. |
M and R exert the same impulse on T. |
b. |
M
exerts a greater impulse on T than R does. |
c. |
R exerts a greater impulse on T than M does. |
d. |
The
magnitudes of the change in momentum of M and R are equal. |
e. |
none of these |
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19. |
Two
protons approach one another in a straight line with equal speeds. Eventually,
they repel, and move apart with equal speeds in the same straight line.
At the instant of minimum separation between the particles
a. |
the
total momentum of the interacting particles is zero, but the total
energy of the system remains constant |
b. |
both the total momentum and the total energy are
zero |
c. |
the
total momentum of the system is at the maximum value, but the
total energy is zero |
d. |
both
the total momentum and the total energy of the system are at their
maximum values |
e. |
both
the total momentum and the total energy of the system are reduced,
but not to zero |
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Figure 2
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20. |
A
ball bounces off the edge of a pool table as in Figure 2. The
speeds before and after the bounce are essentially equal. Which of the
five vectors in Figure 2 represent the direction of the impulse
by the table on the ball?
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21. |
A
glider of mass m travels leftward on a frictionless air track
with a speed v. It collides head-on in a completely inelastic
collision with a glider that has twice its mass and half its speed moving
to the right. After the collision, the combined speed of the glider
system is
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22. |
A
baseball of mass m leaves a pitching machine of mass M
(where M includes the mass of the ball m) with a speed
v. The recoil speed of the machine after shooting the baseball
is
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