1' 10 points

1
1. (10 points) A softball (mass 185 g, radius
4.85 cm, I 1.74 x 10-4 kg?m2) rolls without
slipping on a field with a linear speed of 18
m/s. What is the total kinetic energy of the
ball? (a) 0.31 J (b) 12 J
(c) 30 J (d) 42 J
(e) 81 J
2

• 2. (10 points)
• Three particles, each of which has a mass of 40
  g, are positioned at the vertices of an
  equilateral triangle with sides of length 60 cm.
  The particles are connected by light rods. What
  is the moment of inertia of this rigid body about
  an axis marked as X that is perpendicular to
  the plane containing the three particles and that
  passes through the midpoint of one of the sides
  of the triangle?
• 0.018 kg?m2 (b) 0.022 kg?m2 (c) 0.015 kg?m2
  (d) 0.026 kg?m2
• (e) 0.012 kg?m2

3
3. (10 points) A golf ball is a small solid
sphere. A volleyball is a hollow sphere that is
filled with air. A bicycle tire is a large
rubber hoop-like object. If all three objects
are released at the same instant at the top of an
inclined plane and allowed to roll to the bottom,
what is the order of finish? (a) golf ball,
volleyball and bicycle tire (b) bicycle tire,
volleyball, golf ball (c) volleyball, golf ball,
bicycle tire (d) volleyball, bicycle tire, golf
ball (e) golf ball, volleyball, bicycle tire
4
(4) (10 points) The engine of my BMW produces
maximum torque of 245 N?m at a speed of 4200 rpm.
What is the power this engine produces when
it produces maximum torque? (a) 84 kW
(b) 91 kW (c) 108 kW
(d) 77 kW (e) 121 kW  
5
5. (10 points) A horizontal platform in the
shape of a circular disk rotates about a
frictionless vertical axle through the center of
the disk. The platform has a mass of 150 kg, a
radius of 2.0 m. A 60-kg student initially is
standing at the rim of the disk. At this point
the motor driving the platform is turned off and
no external forces act on the system. The
angular speed of the disk was 2.0 rad/s when the
motor turned off. How much work does the student
do to walk from the rim to the center of the
disk? (a) 700 J (b) 912 J
(c) 443 J (d) 864 J
(e) 1200 J
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6. (10 points) A CD disk has a radius of 6.0 cm
and a mass of 16 g. Its moment of inertia is
therefore 2.9 x 10-5 kg-m2. A certain CD player
reaches it operating speed of 486 rpm in 0.40 s
from rest. What constant torque did the motor
produce? (a) 3.7 mN-m (b) 0.22 N-m
(c) 0.59 mN-m (d) 1.3 N-m (e)
0.47 N-m
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7. (10 points) A large wooden disk has a mass of
50 kg and a radius of 90 cm. The disk rotates
about an axis that is perpendicular to the disk
and passes thru a point that is halfway between
the center of the disk and the rim. What is the
moment of inertia of the disk about this
axis? (a) 20 kg-m2 (a) 51 kg-m2
(a) 26 kg-m2 (a) 41 kg-m2
(a) 30 kg-m2
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8. (10 points) A mass of 5.0 kg is attached to a
string that is wound around a hollow cylinder of
radius 10 cm. When released from rest the
acceleration of the mass is 7.0 m/s2. What is
the mass of the cylinder? (a) 4.0 kg
(b) 2.0 kg (c) 3.0 kg
(d) 4.5 kg (e) 2.5 kg
5 points for (a) wrong I for pulley
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9. (10 points) A 3.5-kg rod has a length of 80
cm. It is pivoted about a pin in one end. The
rod is released from rest when it is positioned
20? below the horizontal as shown. What is the
initial angular acceleration of the rod? ( Note
Icm ML2/12) (a) 18.4 rad/s2 (b) 69.1
rad/s2 (c) 6.31 rad/s2 (d) 8.40
rad/s2 (e) 17.3 rad/s2
5 points for (b) wrong I
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10. (10 points) A 60-g particle moves with a
velocity of (40i 30j) m/s. The path of the
particle crosses the x-axis at x 2.0 m. What
is the magnitude of the angular momentum of this
particle about the origin? (a) 4.8 kg-m/s
(b) 6.0 kg-m/s (c) 3.6 kg-m/s (d)
2.4 kg-m/s (e) 1.8 kg-m/s