Originally Posted by
Chu Chu
If I'm walking down the side of the road, I can calculate my kinetic energy relative to the ground surface, or relative to the truck that's coming the other way. It's only the first that matters . . . unless I step in front of the truck.
and if you *do* step in front of the truck your change in kinetic energy in the frame of reference of the ground will be identical to your change in kinetic energy relative to the frame of reference of the truck.