Which is a better conductor of heat: air or a copper wire? why?
a) air is a better conductor of heat because it is a mixture.
b) copper is a better conductor of heat because it contains electrons.
c) air conducts heat better because the molecules in a gas are further apart.
d) copper wire conducts heat better because molecules in a solid are closer together.

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point