Eli5: how can you roll start a manual vehicle but not an automatic vehicle?
In: Other
At a more basic level, an engine when it is turning is doing several things at once. The turning motion pushes and pulls pistons in and out of cylinders. When a piston is being pulled, air and fuel gets sucked into the cylinders, and a spark is generated. That spark ignites the air and fuel, pushing the piston down. That action keeps is what keeps the engine turning. So it’s all a self-sustaining process you just have to get it going. Its the same thing on airplanes when someone in an old movie spins the propeller by hand to start the engine. Modern airplanes work the same way, there is now just a little electronic motor to provide the initial spin so no one gets their hand chopped off. Then the engine just does it’s thing.
As others point out, automatic cars have extra layers between the engine and the wheels turning so pushing the car doesn’t turn the engine the same way.
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