why can cars be fast and slow?

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frollard8 years ago
The engine (speed via throttle), Engine speed, depending on the model can range from as low as 30 rpm (giant cruise ship engines) to 20000 rpm (indy car).
The transmission (gear ratio) means the engine can do x speed, and the wheels will do a ratio of x. First gear the engine turns faster than the wheels, and in overdrive (top gear) the wheels turn faster than the engine - so the engine can always operate in its 'power band' of rpm, while the car does various speeds.

and in automatic transmission cars:
A torque converter, which is like a slippery clutch that takes variable speed power at one end and spins the other end when power is applied, but slips when power is not applied, allowing the car to freewheel, and the car to be still while the engine idles.

Specifically to get from fast to slow: Brakes are very important. They convert motion into heat via friction.
Kiteman8 years ago
Because the car-making men like them that way.
With plenty of planned obsolescence. Once the ticking timer finds it's way to 0, the cars break and go slow.
There are many variables. The type of engine, gas, how much you put the pedal to the metal, how heavy the car is (Hummer slower than corvette) and if you are pretending or not.
lemonie8 years ago
Old people can't depress the accelerator very well, or remember to take the handbrake-off = slow.
Young guys have long legs and heavy boots, so they floor-it = fast.

NachoMahma8 years ago
. The throttle is used to vary engine speed by adjusting the air/fuel flow.
They're capable of producing different rates of speed according to the operation of their engines.