Tritium has a half-life of 12.3 years. What proportion of its original radioactivity will a sample have after 6 years?
a. 0.55
c. 0.84
b. 0.60
d. 0.71
D
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A future news release might report that a new planet has been found around a star very similar to our Sun. The system contains other planets as well like our solar system. This newly discovered planet is claimed to have a mass 40 times that of Earth and is located nearly 25 AU from the star it orbits. Which of the following would be a reasonable prediction about this planet, assuming it formed
like our solar system? I. The planet will probably have a mean density of around 5 g/cm3. II. The planet will probably have a radius of around five to ten times greater than Earth's. III. The planet will probably have several satellites. IV. The planet will probably have a composition that is mostly hydrogen and helium. a. I & IV b. I, II, & III c. II, III, & IV d. I, II, & IV e. I, II, III, & IV
Series/Parallel Circuits: Four resistors having resistances of 20 ?, 40 ?, 60 ?, and 80 ? are connected in series across an ideal dc voltage source. If the current through this circuit is 0.50 A, what is the voltage of the voltage source?
A. 20 V B. 40 V C. 60 V D. 80 V E. 100 V
The intensity of the sound wave from an airplane is
at 5.0 m. What is the intensity at 100 m?
A. 0.25 
B. 0.53 
C. 5.0
D. 0.25 
Unbalanced torques produce rotational accelerations, and balanced torques produce rotational equilibrium
Indicate whether the statement is true or false