What is so unique about the mirrors of telescopes such as the Keck Observatory, Gran Telescopio Canaries and the soon-to-be-built Giant Magellan Telescope?
a. The mirrors are made of a newly designed metallic material.
b. The mirrors can fold up went not in use
c. The mirrors are inexpensive.
d. The mirrors are segmented.
e. The mirrors are thin.
d
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Conversion of Units: Wall posters are usually sold curled up in cylindrical cardboard tubes. If the length of the tube is 0.845 m, and the inside diameter of the tube is 2.40 mm, what is the area of the poster expressed in square centimeters to the correct number of significant figures? (Assume the poster is just as long as the tube and does not overlap itself.)
A. 202.8 cm2 B. 637.1 cm2 C. 203 cm2 D. 319 cm2 E. 637 cm2
Coulomb's Law: A point charge Q = -12 ?C, and two other charges q2 and q2, are placed on x-y axes as shown in the figure. The electric force components on charge Q are Fx = +0.005 N and Fy = -0.003 N. (k = 1/4??0 = 9.0 × 109 N ? m2/C2, e = 1.6 × 10-19 .C(a) How many excess electrons are there in charge Q?(b) What are the charges q1 and q2, including their signs?
What will be an ideal response?
A car accelerates from rest to 30 km/h. Later, on a highway it accelerates from 30 km/h to 60 km/h. Which takes more energy, going from 0 to 30, or from 30 to 60?
(a) 0 to 30 km/h. (b) 30 to 60 km/h. (c) Both are the same.
What is one of the differences between Cepheids and RR Lyrae variables?
A) The period-luminosity relation holds only for RR Lyrae stars. B) The pulsations of RR Lyrae stars are much less regular than those of Cepheids. C) Cepheids are giants, but RR Lyrae stars are still on the main sequence. D) All Cepheids have the same brightness, but RR Lyrae stars vary greatly in luminosity. E) The RR Lyrae stars have much shorter periods than Cepheids.