Why the polarity of the hall voltage changes depending on the conductivity of the semiconductor

An ionic compound can conduct electricity when a it is dissolved in water b its crystals are ground into powder c it is in solid form d it is heated to just below its melting point

Arailroad car collides with and sticks to an identical railroad car that is initially at rest. after the collision, the total kinetic energy of the two cars is a) the same as before. b) half as much as before. c) one third as much as before. d) one fourth as much as before. e) twice as much as before.

Which best describes the weak nuclear force? it maintains attraction between the m ecules in liquids. it attracts the nucleus of one atom to the nucleus of another atom. it pulls all matter in the universe together it keeps particles that make up protons and neutrons together