If the accelerator changes a body's velocity and turning it and bringing it a fixed point results in a constant velocity, this means that the force being exerted is equal to the kinetic frictional force. However, if the scooter goes from a smooth surface to a rough surface, keeping the accelerator at the same fixed point, the velocity reduces but still remains constant after that. But the friction offered by the rough surface is more, therefore to maintain a constant velocity, the force exerted needs to be increased. But since we haven't made any changes on our part, (we're keeping the the accelerator at the same point) this means that the scooter recognized the new friction itself and increased the force itself to maintain constant velocity. Does this mean that the scooter can recognize friction offered itself? Or maybe the accelerator doesn't exactly control the velocity but some other quantity? Or is my observation wrong and when we go on to the rough surface, the velocity decelerates to zero?
closed as unclear what you're asking by sammy gerbil, ZeroTheHero, Jon Custer, John Rennie, Kyle Kanos Aug 25 '17 at 10:01
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When analyzing vehicle dynamics, we often assume that the friction is static friction.
That represents a scenario where the wheels are in "pure rolling" (they don't slide/slip). The point of contact with the ground is stationary relative to the ground, and movement comes from the wheel turning, and having a new part of the wheel in contact with the ground. There is never slipping between the two, so it is purely static friction.
If we assume this is pure rolling, the tires do not slip. In that scenario, the friction has to be high enough so that we don't start slipping instead of rolling.
The static friction doesn't actually need to change when going between surfaces as long as both can provide enough static friction to avoid slipping.
Therefore, as long as the wheels stayed in approximately pure rolling, the surface should not make it any more difficult to drive.
If the surface had too little friction, you might notice.
No your scooter cannot detect rough ground - unless it is 'smart' like your 'phone.
You seem to be confused about what the accelerator does. It does not keep the scooter's velocity constant, and it does not exert a constant force. It controls the power output of the engine.
If the accelerator setting is fixed, then the power output of the engine is (approximately) constant. Engine power = resistance force x velocity, provided that the velocity is not changing. If the resistance force doubles then the velocity of the scooter halves.
The force opposing the motion of rolling wheels is usually called rolling resistance. It is not strictly kinetic friction, which applies to sliding objects.