A horizontal disk with moment of inertia I1 rotates with angular speed ?1 about a vertical frictionless axle. A second horizontal disk, with moment of inertia I2 drops onto the first, initially not rotating but sharing the same axis as the first disk. Because their surfaces are rough, the two disks eventually reach the same angular speed ?. The ratio ?/?1 is equal to
1. I1 / I2
2. I2 / I1
3. I1 / (I1 + I2)
4. I2 / (I1 + I2)
3
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A transformer has 200 turns on its primary and 12 turns on its secondary. If the input voltage is 2000 V, what is the output voltage?
A. 
B. 240 V
C. 170 V
D. 120 V
E. 100 V
Water is flowing through a pipe with a constriction. The area of the narrow section is one-half the area of the wide section. If the velocity of the incompressible fluid is 3.2 m/s in the wide section, then what is the velocity of the fluid in the narrow section?
A. 6.4 m/s B. 5.9 m/s C. 5.0 m/s D. 4.7 m/s E. 4.2 m/s
Our textbook discusses the cosmic calendar, a model of the history of the universe scaled to a single year. The length of time represented by one month on this cosmic calendar is therefore
A) about ten million years. B) about one million years. C) about one billion years. D) about ten billion years. E) about 1000 years.
A 5.0-kg object is pulled along a horizontal surface at a constant speed by a 15-N force acting 20° above the horizontal. How much work is done by this force as the object moves 6.0 m?
a. 78 J b. 82 J c. 85 J d. 74 J e. 43 J