A radioactive substance is placed in a sealed container. Three days later, only one-eighth of the sample is still radioactive. What is the half-life of the sample?
A. 4 days
B. 2 days
C. 1 day
D. 12 hrs
E. 6 hrs
C. 1 day
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Which of the following is NOT one of the four stages in the development of a terrestrial planet?
a. flooding b. cratering c. slow surface evolution d. fusion of hydrogen to helium e. differentiation
Two objects are dropped from a bridge, an interval of 1.0 s apart, and experience no appreciable air resistance. As time progresses, the DIFFERENCE in their speeds
A) increases. B) remains constant. C) decreases. D) increases at first, but then stays constant. E) decreases at first, but then stays constant.
A 400-turn circular coil (radius = 1.0 cm) is oriented with its plane perpendicular to a uniform magnetic field which has a magnitude that varies sinusoidally with a frequency of 90 Hz. If the maximum value of the induced emf in the coil is observed to be 4.2 V, what is the maximum value of the magnitude of the varying magnetic field?
a. 59 mT b. 62 mT c. 65 mT d. 68 mT e. 31 mT
An electron and a proton are each released from rest in the same uniform electric field. The electron moves a distance delectron and the proton moves a distance dproton as each particle's kinetic energy increases by 1.6 eV. How do delectron and dproton compare?
a. delectron > dproton b. delectron = dproton c. delectron < dproton d. The answer depends on the direction of the electric field.