The half-life of 131I is 8 days. On a certain day, the activity of an 131I sample is 6.4 mCi. What is its activity 40 days later?
200 ?Ci
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On a scale in which the distance from Earth to the Sun is about 15 meters, the distance from Earth to the Moon is ________
A) about 30 meters B) small enough to fit within your hand C) about 1 meter D) about 5 meters
A uniform, solid, cylindrical flywheel of radius 1.4 m and mass 15 kg rotates at What is the magnitude of the flywheel's angular momentum?
A) 60 kg ? m2/s B) 80 kg ? m2/s C) 40 kg ? m2/s D) 20 kg ? m2/s
If an unbalanced force applied to an object doubles, then
A. its acceleration is cut in half B. its acceleration doubles C. its velocity doubles D. its acceleration increases by a factor of four
How was the first asteroid discovered?
A. Newton inferred their existence by their gravitational influence on Jupiter. B. Kepler traced back the path of meteors to the Asteroid belt. C. Galileo saw it whiz by Jupiter. D. It collided with the Moon. E. Piazzi found it by searching for objects at the distance suggested by Bode's law.