e=mc^2 is the sort form of an equation that includes velocity. Getting a 6 year old to understand energy takes a sloped hill and tossing balls up it. The harder you throw the ball the farther up the hill it goes and the faster it is when it rolls back. To talk about mass take a heaver ball and get the idea that how far up the hill something is * how heavy it is gives some idea how much energy it has at the end. Say knocking stuff over or hitting a wall of sand.
Then describe mass as having energy like a being on top of a vary big hill. If you converted a little bit of mass into energy you have a really fast ball. Like a big ball that's 1/2 way down the really big hill.
This of course assumes an intelligent 6 year old. But, the expression is talking about some six year old not, all of them. You may need to talk about wind resistance as well, but there are some vary good demonstrations for that: http://www.youtube.com/watch?v=ndFXXasM6ZE
PS: Honestly, I think after that discussion your intelligent six year old would probably understand it better than your average high-school or even collage student who has no clue there is more than just e=mc^2.
Then describe mass as having energy like a being on top of a vary big hill. If you converted a little bit of mass into energy you have a really fast ball. Like a big ball that's 1/2 way down the really big hill.
This of course assumes an intelligent 6 year old. But, the expression is talking about some six year old not, all of them. You may need to talk about wind resistance as well, but there are some vary good demonstrations for that: http://www.youtube.com/watch?v=ndFXXasM6ZE
PS: Honestly, I think after that discussion your intelligent six year old would probably understand it better than your average high-school or even collage student who has no clue there is more than just e=mc^2.