What happens when you change gears with a manual car? Like what happens that allows the car run better and go faster?
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Same thing as when you change into a different gear on your bicycle.
If you turn a crank with your hand, for every time your hands move the handle around, the crank goes around once. If your crank has gear teeth and drives another same size gear, every time you move your handle around the other gear will go around once.
If the other gear has more teeth (generally because its larger), for a single rotation of your crank, that other gear won’t go a full revolution. If the other gear has less teeth (smaller), then for every rotation of your crank the other gear will go more than a rotation. In general when one gear drives another gear that is larger and slower, its less work to turn the crank. Conversely driving a gear that is smaller is more work (this is all assuming there’s a load on that 2nd gear, like the rest of a bicycle and you’re pedalling.)
Modern car engines are designed to do their best work within a certain range of RPMs, but that goes contrary to what speed the car is going at – i.e.. how fast the wheels are spinning. So what a car transmission does is attempt to change the gear ratio between the engine and the wheels so that the engine is always driving the wheels within its best RPM range.
In a manual car, shifting into 1st gear is like the engine turning the crank one and the wheel rotating 1/2 way. 2nd gear might be the engine turning once and the wheels going around once. WHen the car isn’t moving very fast, this makes the car easier to “pedal” for the engine; so good to accelerate quickly or do harder work like going up a hill; just like you on your bicycle. At high speeds though if you were in a very low gear the number of times your engine has to turn is super high (and high RPMs makes your engine explode). So generally “higher” gears at higher speeds are where your engine turns once and the wheels turn more than once (i.e. your “gear ratio” is higher: 1:2 – for every turn of the engine the wheels turn 2 times). Its a little harder to pedal that fast if you want to accelerate, but it keeps your engine running at lower RPMs than your wheels are spinning.
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