I used to believe that various cars with exhaust pipes (tailpipes) when the smoke came out, that's what made the car move. i.e. if tailpipe came straight out the back, that made the car go FAST, if it came out to the side, means it went SLOW.
A childhood belief about cars

others believed things like this
- I used to believe that car exhaust pipes were what propelled cars, instead of the engines.— Thomas Johnston
- I thought that people were like cars because cars have exhaust pipes, and people fart.— Matt
- That all clouds were made by aeroplane exhaust fumes— diyjoe.com
- I used to think that cars were powered by a jet of air which came out of the exhaust.— BadDeal
- I used to believe that cars were propelled by their exhaust like some kind of rocket.Anon
- Some sport cars have a double exhaust. I wondered why. Why would people want to pollute twice as much?— F*ck the environment?