Found a rough surface 9" diameter rock in glacier forest upper wisconsin
it is within like 5/8 from being totally round with a dimple on each side very coarse surface, could not get xray of a 1 second time to show anything does anybody have a theory on how it came to be shis shape.

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.