At Chernobyl, one of the harmful radioactive isotopes was 131I, a beta emitter with a halflife of 8 days. Suppose some of this isotope is deposited on a field. What can we say about this field 40 days later?
A) It is just as radioactive as it was to begin with.
B) Its radioactivity has decreased to harmless levels.
C) Its radioactivity level has decreased to 1/32 of its original level.
D) Its radioactivity level has decreased to 1/16 of its original level.
E) Its radioactivity level has decreased to 1/64--one sixty-forth--of its original level.
C
You might also like to view...
If the collision is completely inelastic, how many quantities suffice to determine the system’s final state?
A. Zero B. One C. Two D. Three E. Four
If a dense 20.0-kg object is falling in air at half its terminal velocity, what is the drag force on the object at this moment?
A. 24.5 N B. 49.0 N C. 69.3 N D. 98.0 N E. 139 N
Air is pumped into a bicycle tire at constant temperature. The pressure increases because:
A. more molecules strike the tire wall per second B. the molecules are larger C. the molecules are farther apart D. each molecule is moving faster E. each molecule has more kinetic energy
An object is rotating with an angular momentum 4.00 kg ? m2/s while being acted on by a constant torque 3.00 N ? m . What is the angular speed of precession of the angular velocity of the object?
A) 1.33 rad/s B) 0.750 rad/s C) 12.0 rad/s D) zero E) It depends on the moment of inertia of the object.