The typical density of a solid metal is 2700 kg/m3 and the density of air is 1.3 kg/m3.

Approximately how many times more dense is a solid compared to a gas?

1) 2.7
2) 800
3)3510
4)2077

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.