If one object is hot and another one cold, thermal energy
a: will move from the cold object to the hot one.
b: will move from the hot object to the cold one.
c: will move back and forth between the hot and cold objects.
d: will not move at all.

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.