Two wires A and B with circular cross sections are made of the same metal and have equal lengths, but the resistance of wire A is three times greater than that of wire B. What is the ratio of the radius of A to that of B?
1.3
2.?3
3.1
4.1/?3
5.1/3
4
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If you could convert the entire mass of the Sun (mass 2 x 1033g) into pure energy, how much energy would be produced (in ergs) ? The speed of light c = 3 x 1010cm/s.
A. 2 x 1033ergs B. 1.8 x 1054ergs C. 6 x 10133ergs D. 1 x 1051ergs E. 6 x 1043ergs
A hologram is simply a
A) complex diffraction grating. B) thin sheet of non-cubic transparent crystals. C) pair of semi-crossed polarization filters. D) thin photographic film with microscopic images over the entire surface. E) none of the above
On its own, a certain tow-truck has a maximum acceleration of 3.0 m/s2. What would be the maximum acceleration when this truck was towing a bus of twice its own mass?
A) 2.5 m/s2 B) 2.0 m/s2 C) 1.5 m/s2 D) 1.0 m/s2
This visible-light photo shows a starburst galaxy. What is going on with the reddish gas that seems to be emerging on both sides of it?
A) It is gas being blown out in a galactic wind. B) It is gas from a protogalactic cloud that is still falling inward toward the galactic center. C) The gas represents jets being shot out from the region of a supermassive black hole. D) The gas consists of many individual stars that are bursting out from the central regions of the galaxy.