PHYSICS 221 - SPRING 2001 - Final Exam - 1 May 2001
51. An "electron-volt" is
(A) the force acting on an electron in a field of 1 N/C
(B) the force required to move an electron 1 meter
È(C) the energy gained by an electron in moving through a potential difference of one
volt.
(D) the energy needed to move an electron through one meter in any electric field.
(E) the work done when one coulomb of charge is moved through a potential difference of
one volt.
52. A solid metal sphere carries a charge of 5 d 10c9 C and is at a potential of
relative to the potential at infinity. The potential at the center of the sphere is:
È(A) 400 V (B) c 400 V
(E) 8 d 1010 V
(C) 2 d 10c6 V
400 V,
(D) 0
53. Three charges lie on the % axis: 1 C at % ~ 1 cm, 2C at % ~ 2 cm, and 3C at
% ~ 3 cm. The potential energy of this arrangement, relative to the potential energy for
infinite separation, is:
(A) 800 J
(B) 8 J
(C) 0.08 J
(D) 0.016 J
(E) 0
54. The diagram shows six 6 F
capacitors. The capacitance between
points A and B is
(A) 3 F
È(B) 4 F
(C) 6 F
55. Three electric charges b Á b 8Á
and c 8 are placed, as shown, at the
vertices of an equilateral triangle lying in
a vertical plane. The net force on the
charge b due to the other two charges
is
(A) vertically up
(D) horizontal to the left
(D) 9 F
(A) 2 F
l b
l b8
(B) vertically down
(C) zero
È(E) horizontal to the right
m c8
56. A battery is used to charge a parallel-plate capacitor, after which it is disconnected.
Then the plates are pulled apart to twice their original separation. This process will double
the:
(A) capacitance
È(C) stored energy
(E) charge on each plate
(B) surface charge density on each plate
(D) electric field between the plates
57. Which of the following would have the largest capacitance when placed between two
metal sheets?
(A) a 1.0-mm gap of air
È(B) a 0.1-mm thickness of mica ( ~ 6)
(C) a 2.0-mm thickness of glass ( ~ 7)
(D) a 1.0-cm thickness of paraffin ( ~ 2)
(E) a 10-cm thickness of a dielectric with ~ 10
58. A 10-+ resistor has a constant current of 5 A. How many coulombs of charge flow
through this resistor during in 4 minutes?
(A) 20
(B) 40
(C) 200
È(D) 1200
(E) 2400
59. Of the following, the copper conductor that has the least resistance is
(A) thin, long, and hot
È(B) thick, short and cool (C) thick, long, and hot
(D) thin, short, and cool
(E) thin, short, and hot
60. A nichrome wire is 1.0 m long and 1.0 mm2 in cross-sectional area. When connected to
a potential difference of 2.0 V, a current of 4.0 A exists in the wire. The resistivity of the
nichrome is
(A) 1 d 10c7 +-m
È(D) 5 d 10c7 +-m
(B) 2 d 10c7 +-m
(E) 8 d 10c7 +-m
(C) 4 d 10c7 +-m
61. Nine identical wires each of diameter and length 3 are connected in series. The
combination has the same resistance as a single wire of length 3 but whose diameter is:
(A) 9
(B) 3
È(C) °3
(D) °9
(E) °81
62. If an emf of 110 V develops 12 W of power in a resistance across which it is placed,
what will be power when an emf of 220 V is placed across it?
(A) 3 W
(B) 6 W
(C) 12 W
(D) 24 W
È(E) 48 W
63. 3.0-+ and 1.5-+ resistors are wired in
parallel and the combination is wired in
series to a 4.0-+ resistor and a 10-V emf
device, as shown. The potential difference
across the 3.0-+ resistor is:
È(A) 2.0 V
(B) 6.0 V
(C) 8.0 V
(D) 10 V
(E) 12 V
64. In the circuit shown, the capacitor is
initially uncharged. At time ! ~ 0, switch S
is closed. If denotes the time constant, the
approximate current through the 3.0-+
resistor when ! ~ °100 is:
(A) 3°8 A
(B) 1°2 A
(C) 3°4 A
È(D) 1 A
(E) 1.5 A
65. Which one of the following statements is false?
(A) The equivalence capacitance of two or more capacitors connected in series is always
less than the smallest capacitance in the group.
(B) The equivalence resistance of two or more resistors connected in parallel is always less
than the smallest resistance in the group.
(C) In a superconductor a current can persist without any applied voltage.
(D) The two headlights on a car are wired in parallel.
È(E) If the electric field is zero in some region of space, the electric potential must also be
zero in that region.
66. A boy is pulling a wooden box along a
rough horizontal floor at constant speed by
W as shown in the diagram.
means of a force 7
Which of the following must be true?
(A) 7 € and 5 ~ (C) 7 ~ and 5 ~ (E) 7 ~ and 5 € È(B) 7 € and 5  (D) 7 ~ and 5  67. In which graph is the particle the farthest from the origin at ! ~ 5 s?
(A) Graph a (B) Graph b (C) Graph c (D) Graph d È(E) Graph e
68. An object of mass 2 is attached by a
rope to another object of mass , as
shown. A force of magnitude 7 acts on
the lighter object to accelerate the system.
The tension ; in the rope acting on the
heavier object is:
È(A) 27 °3 (B) 7
(C) 27
(D) 37
(E) 37 °2
69. A golfer drives her ball from the tee a distance of 100 meters down the fairway in a
high arching shot. When the ball is at the highest point of its flight
(A) its velocity and acceleration are both zero.
(B) its velocity is zero but its acceleration is nonzero.
(C) its velocity is nonzero but its acceleration is zero.
È(D) its velocity and acceleration are both nonzero.
(E) none of the above.
70. A He4 nucleus (atomic mass 4) moving
3W
#
with speed # breaks up into a neutron
§
(atomic mass 1) and a He3 nucleus (atomic He4 k TTS #W À À À À À À k n
mass 3). The neutron moves off at right
k
angles to the original He4 nucleus a shown. If
He3
the neutron speed is 3#, the final speed of the
He3 nucleus is:
(A) 0
(B) #
(C) 4#°3
È(D) 5#°3
(E) l 10 #
71. A block of mass and initial speed #0
slides along a track from one level to a higher
level as shown. What is the speed of the
block at point C?
(A) m ²#0 ³2 b 4/
(B) m ²#0 ³2 b 2/
È(D) m ²#0 ³2 c 4/
(C) l 3/
(E) m ²#0 ³2 c 2/
72. A 2.5-kg stone is released from rest and falls toward the Earth. After 4.0 s its linear
momentum has the magnitude (in kg-m/s):
È(A) 100
(B) 80
(C) 50
(D) 25
(E) 0
73. Suppose a planet exits that has half the mass of the earth and half its radius. On the
surface of that planet, the accleration due to gravity is
È(A) twice that on earth
(C) half that on earth
(E) none of these is correct
(B) the same as that on earth
(D) one-fourth that on earth
74. A block of mass slides on a frictionless
surface along a loop-the-loop shown in the
figure. Which free body diagram is correct
for the block when it is located at point D?
§
(A)
¨
È(B)
¨ ¨
§
(C)
¨
(D)
§
¨
(E) RT ¨
75. A mass-spring system and a simple pendulum each have a period of one second on
earth. Both are taken to the moon in a lunar landing module. While they are inside the
module on the surface of the moon
(A) the pendulum has a period shorter than one second
(B) the mass-spring system has a period shorter than one second
È(C) the pendulum has a period longer than one second
(D) the mass-spring system has a period longer than one second
(E) the periods of both are unchanged
There were also some multiple-choice lab questions on this exam.