Name __________________________________________
AP Physics Summer Work
Rotational Mechanics – Angular Momentum
(1)
If the angular momentum of a system is constant, which of the following statements must
be true?
A) A constant torque acts on each part of the system.
B) Zero net torque acts on each part of the system.
C) A constant external torque acts on the system.
D) Zero net torque acts on the system.
1) ______
(2)
The angular momentum of a flywheel about its axis is 925 kg-m2/s. If its moment of
inertia about the same axis is 2.50 kg-m2, its angular velocity is what amount?
A) 370 rev/min
B) 62 rev/min
C) 2210 rad/s
D) 370 rad/s
2) ______
(3)
To increase the moment of inertia of a body about an axis, you must
A) increase the angular acceleration.
B) increase the angular velocity.
C) make the body occupy less space.
D) place part of the body farther from the axis.
3) ______
(4)
A 2.0-g particle moves at a constant speed of 3.0 mm/s around a circle of radius 4.0 mm.
Find the magnitude of the angular momentum of the particle.
A) 2.40  10−6 kg-m2/s
B) 2.40  10−3 kg-m2/s
C) 2.40  10−8 kg-m2/s
D) 2.40  101 kg-m2/s
4) ______
(5)
A 2.0-kg particle moves directly eastward at a constant speed of 4.5 m/s along an east-west
line. What is the magnitude of its angular momentum about a point that lies 6.0 meters
north of the line?
A) 54 kg-m2/s
B) 90 kg-m2/s
C) 27 kg-m2/s
D) 12 kg-m2/s
5) ______
Page 2
(6)
You stand on a frictionless platform that is rotating at an angular speed of 1.5 rev/s. Your
arms are outstretched, and you hold a heavy weight in each hand. The moment of inertia of
you, the extended weights, and the platform is 6.0 kg-m2 . When you pull the weights in
toward your body, the moment of inertia decreases to 1.8 kg-m2. What is the resulting
angular speed of the platform?
A) 5 rev/s
B) 0.2 rev/s
C) 0.5 rev/s
D) 3.33 rev/s
6) ______
(7)
A skater is spinning at 32.0 rad/s with her arms and legs extended outward. In this position 7) ______
her moment of inertia with respect to the vertical axis about which she is spinning is
45.6 kg-m2. She pulls her arms and legs in close to her body changing her moment of inertia
to 17.5kg-m2. What is her new angular velocity?
A) 14.6 rads/s
B) 83.4 rad/s
C) 12.3 rads/s
D) 56.0 rad/s
(8)
Say that NASA planned to put a satellite into a circular orbit around Pluto for studies, but
8) ______
the situation got a little out of hand and the satellite ended up with an elliptical orbit. At its
nearest point to Pluto, 6.6106 meters, the satellite zips along at 9,000 meters per second.
At its farthest point the satellite is 2.0107 meters. What is its speed at this farthest location?
A) 2970 m/s
B) 980 m/s
C) 3300 m/s
D) 2700 m/s
(9)
Calculate the angular momentum of a phonograph record (LP) rotating at 33 1 /3 rev/min.
An LP has a radius of 15 cm and a mass of 150 grams.
A) 3.49  10−1 kg-m2/s
B) 1.18  10−2 kg-m2/s
C) 5.89  10−3 kg-m2/s
D) 3.38  10−3 kg-m2/s
(10)
A cylinder of mass 250 kg and radius 2.60 m is rotating at 4.00 rad/s on a frictionless surface 10) ______
when two more identical nonrotating cylinders fall on top of the first. Because of friction
between the cylinders they will eventually all come to rotate at the same rate. What is this
final angular velocity?
A) 1.33 rads/s
B) 7.50 rad/s
C) 3.75 rads/s
D) 0.75 rad/s
9) ______
Page 3
(11)
A person stands, hands at his side, on a platform that is rotating at a rate of 1.3 rev/s. If he
raises his arms to a horizontal position, the speed of rotation decreases to 0.80 rev/s.
By what factor has the moment of inertia of the person changed?
A) 1.3 times more
B) 1.6 times more
C) 0.62 times more
D) 0.62 times less
11) ______
(12)
A figure skater can increase her spin rotation rate from an initial rate of 1.0 revolution every 12) ______
2 seconds to a final rate of 3.0 rev/sec. If her initial moment of inertia was Ii =4.6 kg-m2 what
is her final moment of inertia If ?
A) 27.6 kg-m2
B) 2.76 kg-m2
C) 0.77 kg-m2
D) 0.17 kg-m2
(13)
A 15 gram paper clip is attached to the rim of a phonograph record with a radius of 30 cm
spinning at 3.5 rads/sec. What is the magnitude of the paper clip’s angular momentum?
A) 1.4  10−3 kg-m2/s
B) 4.7  10−3 kg-m2/s
C) 1.6  10−2 kg-m2/s
D) 3.2  10−1 kg-m2/s
(14)
The entrance of a science museum features a funnel into which marbles are rolled one at
14) ______
a time. The marbles circle the wall of the funnel, eventually spiraling down into the neck
of the funnel. The internal radius of the funnel at the top is 0.54 m. At the bottom, the
funnel’s neck narrows to an internal radius of 0.040 m. A 2.510−2 kg marble begins rolling
in a large circular orbit around the funnel’s rim at 0.35 rev/s. If it continues moving in a
roughly circular path, what will the marble’s angular speed be as it passes through the neck
of the funnel?
A) 133 rads/s
B) 525 rad/s
C) 375 rads/s
D) 400 rad/s
(15)
A 15.0 kg turntable with a radius of 25 cm is covered with a uniform layer of dry ice that
15) ______
has a mass of 9.0 kg. The angular speed of the turntable and dry ice is initially 0.75 rads/s,
but it increases as the dry ice evaporates. What is the angular speed of the turntable once all
the dry ice has evaporated?
A) 6.25 rads/s
B) 1.2 rad/s
C) 0.47 rads/s
D) 18.0 rad/s
13) ______
Page 4
(16)
Calculate the angular momentum of Earth that arises from its spinning on its axis.
(Distance from Sun to Earth is 1.50 x 1011 m; Earth mass = 5.98 x 1024 kg;
Sun mass = 1.99 x 1030 kg; Earth radius = 6.37 x 106 m; Sun’s radius = 6.96 x 108 m)
A) 7.05  1033 kg-m2/s
B) 1.69  1035 kg-m2/s
C) 3.25  1034 kg-m2/s
D) 5.84  1033 kg-m2/s
16) ______
(17)
Calculate the angular momentum of Earth that arises from its orbital motion about the sun.
(Distance from Sun to Earth is 1.50 x 1011 m; Earth mass = 5.98 x 1024 kg;
Sun mass = 1.99 x 1030 kg; Earth radius = 6.37 x 106 m; Sun’s radius = 6.96 x 108 m)
A) 2.66  1044 kg-m2/s
B) 1.35  1047 kg-m2/s
C) 2.32  1045 kg-m2/s
D) 2.68  1040 kg-m2/s
17) ______
(18)
A woman sits on a spinning piano stool with her arms folded. When she extends her arms,
which of the following occurs?
A) She increases her moment of inertia, thereby increasing her angular speed.
B) She increases her moment of inertia, thereby decreasing her angular speed.
C) She decreases her moment of inertia, thereby increasing her angular speed.
D) She decreases her moment of inertia, thereby decreasing her angular speed.
18) ______
(19)
A puck on a frictionless air-hockey table has a mass of 0.05 kg and is attached to a cord
19) ______
passing through a hole in the table surface. The puck is originally revolving at a distance of
0.30 m from the hole, with an angular speed 2.50 rads/s. The cord is then pulled from below,
shortening the radius of circle in which the puck revolves to 0.10 m. What is the puck’s
new angular velocity?
A) 7.50 rads/s
B) 8.33 rad/s
C) 22.5 rads/s
D) 27.8 rad/s
(20)
Suppose that our sun runs out of nuclear fuel and suddenly collapses to form a so-called
20) _____
white dwarf, with a diameter equal to that of Earth. Assuming no mass loss, what would be
the sun’s new rotation period (time for one rotation), which is currently about 25 days.
A) 2.25 days
B) 1.65 hours
C) 9.50 min
D) 3.01 min