A convex lens has a focal length f. An object is placed at f on the axis. The image formed is located
A)
at infinity.
B)
between 2f and infinity.
C)
at 2f.
D)
between f and 2f.
E)
between the lens and f.
A
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The general heliocentric model proposed by Copernicus was appealing, and eventually became preferred, because
A. it explained why we do not observe stellar parallax. B. it was more aesthetically pleasing than the complicated Ptolemaic model. C. it made more accurate predictions than the Ptolemaic model. D. it replaced Earth with the Sun as the center of the solar system.
Which of these is the best explanation of the "electric hair" that can occur when some people brush their hair?
A) Excess electrons flow onto both the brush and the hair, causing the hairs to repel each other and causing the brush to repel the hairs. B) The atoms of the brush and hair are set into rapid vibration, causing them to emit electromagnetic waves, which causes the hairs to stand up. C) Electrons are brushed either from the hair onto the brush, or vice-versa, causing the brush and hair to be charged, so that the hairs then attract each other while the brush repels the hairs. D) The atoms of the brush and hair are heated, causing their electrons to move faster, which spreads out the atoms and thus causes the hairs to stand up. E) Electrons are brushed either from the hair onto the brush, or vice-versa, causing the brush and hair to be charged, so that the hairs then repel each other while the brush attracts the hairs.
A resistor, inductor, and capacitor are connected in series, each with effective (rms) voltage of 65 V, 150 V, and 80 V, respectively. What is the value of the effective (rms) voltage of the applied source in the circuit?
a. 295 V c. 96 V b. 48 V d. 88 V
An aircraft flies at an altitude of 20,000 m. With what speed would it fly if M = 1?
(A) 305 m/s (B) 300 m/s (C) 295 m/s (D) 290 m/s