Which of the following properties of a star can be measured directly, during a single night at the telescope?
A) parallax B) distance
C) apparent brightness D) luminosity
C
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A brass rod of length L 5 0.75 m is twisted by torques T until the angle of rotation between the ends of the rod is 3.58. The allowable shear strain in the copper is 0.0005 rad. The maximum permissible diameter of the rod is approximately:
(A) 6.5 mm
(B) 8.6 mm
(C) 9.7 mm
(D) 12.3 mm
In which part of the electromagnetic spectrum have astronomers been unable to get any information?
A) Gamma rays B) X-rays C) Ultraviolet D) Microwaves E) We now can access information in all spectral lengths.
A parallel plate capacitor with plate separation of 4.0 cm has a plate area of 4.0 × 10-2 . What is the capacitance of this capacitor with air between these plates?
A) 8.9 × 10-11 F B) 8.9 × 10-12 F C) 8.9 × 10-13 F D) 8.9 × 10-14 F E) 8.9 × 10-15 F
Two equal positive charges are near each other. If we increase the amount of charge on just one of them, then
A. the strength of the electrical force on both decreases. B. the electric field points toward the larger charge. C. the electric field at the position of the smaller charge increases. D. the larger charge feels a stronger electrical force and the other a weaker electrical force.