A Geiger counter registers a count rate of 8,000 counts per minute from a sample of a radioisotope. The count rate 24 minutes later is 1,000 counts per minute. The half life of the radioisotope is
a. 3 minutes
b. 4 minutes
c. 6 minutes
d. 8 minutes
e. 12 minutes
D
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If the orbit of Mercury were perfectly circular, its rate of precession would be
A) larger than it is now. B) smaller than it is now. C) the same as it is now. D) zero.
In the absence of a greenhouse effect, what would happen to Earth's oceans?
a. They would evaporate. b. They would freeze over. c. They would be rapidly absorbed into the surface rocks. d. They would dissociate into ozone and hydrogen.
A doubly charged ion with velocity 6.9 × 106 m/s moves in a path of radius 30 cm in a magnetic field of 0.80 T in a mass spectrometer. What is the mass of this ion?
A) 11 × 10-27 kg B) 6.7 × 10-27 kg C) 4.5 × 10-27 kg D) 3.3 × 10-27 kg E) 8.2 × 10-27 kg
Potential of Point-Charges: A +5.0-µC point charge is 12 cm from a -5.0-µC point charge. What is the magnitude of the electric field they produce at the point on the line connecting them where their electric potential (relative to infinity) is zero? (k = 1/4??0 = 9.0 × 109 N ? m2/C2)
A. 0 N/C B. 12.5 MN/C C. 0.75 MN/C D. 25 MN/C E. 1.5 MN/C