Oh dear, another scientific illiterate. I already responded to the water powered car nonsense in another part of this thread. But I'll do it one more time:
When you burn hydrogen you combine it with oxygen in the air to make water vapor. This is the opposite of the reaction in which water is split by electrolysis into hydrogen and oxygen. Burning hydrogen to make water releases energy. Splitting water into hydrogen and oxygen requires the same amount of energy as the burning releases (it's just the reverse reaction). So *all* of the power created by burning hydrogen is consumed by the electrolysis needed to create the hydrogen. There is no power left over for moving the car. Because of inevitable inefficiencies, you'll actually need somewhat more power to do the electrolysis than you can get by burning the hydrogen.
Everybody who plussed up the preceding post must have flunked basic chemistry.
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