If you blow air between a pair of closely-spaced Ping-Pong balls suspended by strings, the balls will swing
A) toward each other.
B) apart from each other.
C) away from the airstream.
Answer: A
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A 2.00-kg mass is placed at (3.00, 4.00) m, and a 3.50-kg mass is placed at (3.00, ?4.00) m. What is the moment of inertia of this system of masses about the z axis?
a. 138 kg·m2 b. 16.5 kg·m2 c. 88.0 kg·m2 d. 49.5 kg·m2 e. 22.0 kg·m2
What evidence suggests that most of the mass of the Milky Way is in the form of dark matter?
A) The orbital speeds of stars far from the galactic center are surprisingly high. B) Although dark matter emits no visible light, we have detected its radio emissions. C) Theoretical models of galaxy formation suggest that a galaxy cannot form unless it has at least 10 times as much matter as we see in the Milky Way disk. D) Our view of distant galaxies is often obscured by dark blotches, which are presumably made of dark matter.
Series/Parallel Circuits: Four resistors are connected across an ideal dc source of V = 8.0 V, as shown in the figure. Assume all resistances shown are accurate to two significant figures. What is the current through the 9.0-? resistor?
A. 1.0 A B. 0.67 A C. 0.50 A D. 0.90 A E. 2.0 A
A baseball is moving in the air along the customary parabola. Ignoring air drag, where is the force on the baseball zero?
a. at the top of the parabola b. just when it has started upward c. where it is about to impact d. nowhere