Which statement describes the use of control rods?
control rods are lowered into the reactor to slow down the reaction by absorbing neutrons.
control rods are lowered into the reactor to speed up the reaction by releasing neutrons.
control rods are raised out of the reactor to slow down the reaction by absorbing neutrons.
control rods are raised out of the reactor to speed up the reaction by releasing neutrons.

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

(a) assume the equation x = at^3 + bt describes the motion of a particular object, with x having the dimension of length and t having the dimension of time. determine the dimensions of the constants a and b. (use the following as necessary: l and t, where l is the unit of length and t is the unit of time.) (b) determine the dimensions of the derivative dx/dt = 3at^2 + b. (use the following as necessary: l and t, where l is the unit of length and t is the unit of time.)

Write down two additional questions about earth's magnetic field that will make your presentation more informative.