Physics 151
Name______________________________
December 4, 2006
Exam #3
Lab Section Number________________
Instructions:
There are 20 multiple choice questions (worth 2 points
each), and 3 work problems (worth a total of 60 points).
You must
answer all questions to receive full credit.
You must show all
equations and substitutions made to obtain your answers for the work
problems.
Write the final answers to the problems with their
respective units in the spaces provided.
Part I
(40)
Part II
(60)
Total
(100)
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Part I: Short Answers
Multiple Choice:
Please write in the letter of the item that
best
answers the question.
1.______ The total angular momentum of a system of particles is
conserved if
(A)
the angular velocities of all particles in the system
are constant.
(B) the angular velocity of the center of mass of the
system is a constant.
(C)
the rotational inertia of the system is a constant.
(D)
the net external torque is zero.
(E)
the net internal torque is zero.
2.______
A particle of mass
m
1
is traveling with constant speed
v
clockwise around a circle of radius
R
1
, in the
xy
plane and
centered at the origin.
A second particle, with mass
m
2
, is
traveling counterclockwise with the same speed around a
concentric circle of radius
R
2
.
The total angular momentum
along the
z
axis about the origin of the twoparticle system
is
(A) zero.
(B) (
m
1
R
1
+ m
2
R
2
)v.
(C) (
m
1
R
1
 m
2
R
2
)v.
(D) (
m
1
R
1
 m
2
R
2
)v.
(E)
(m
1
 m
2
)(R
1
+ R
2
)
.
3.______
A child of mass
m
is running with constant speed
v
along a
straight line that is tangent to the rim of a merrygoround
of radius
R
.
The merrygoround is turning about its center
with constant angular velocity
ω
so that the point on the
rim where the child will jump on is coming toward the child.
The rotational inertia of the merrygoround about its
center is
I
.
The total angular momentum of the system
consisting of the child and the merrygoround, about the
center of the merrygoround, is
(A)
I
ω
.
(B)
I
ω
+ mv
.
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 Winter '08
 Naik
 Physics, Angular Momentum, Force, Mass, Work, Fnet

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