Why a car decelerates after releasing the gas pedal?

[vxr]

Homework Statement

Why car decelerates after releasing the gas pedal?

Relevant Equations

none

After the foot is released from the gas pedal, the car will naturally start decelerating.

From my understanding two things are causing this: air resistance and kinetic friction. From my understanding also, in a vacuum and in a place where gravity is relatively small, the car would not decelerate at all. (putting aside the fact that it probably wouldn't be able to drive forward on a surface at all, I guess)

But can someone give a more detailed explanation?
Two questions mainly:
1. Why exactly air resistance is causing deceleration, or for example due to air resistance free falling object has some critical (maximum) velocity. But why is air doing that? Is it because, well, air is basically bunch of gas atoms that are colliding with a moving object, creating some Force?

2. Why is kinetic friction of tires causing deceleration? From my understanding it's mainly due to force of gravitation, and without gravitation there most likely wouldn't be friction, because there would be no contact force (caused by weight) and no ground reaction force (3rd Newton Law I believe).

I just need some "more formal" explanation on both of my questions. Thank you.

 

[kuruman]

1. You are essentially correct. Think of air as a fluid like water only less dense. To move through it, you need to accelerate it and move it out of your way. That means a force exerted by you on it and a reaction force exerted by it on you. Also, don't forget the less important, but still acting, static buoyant force, the same one that keeps hot air balloons in the air. For "more formal" mathematical treatment, you can do your research, perhaps starting with drag.

2. Start here to learn about rolling resistance.

 

[DaveC426913]

Likely of less relevance to the lesson: the engine revs begin to drop to idle.

 

[haruspex]

Why is kinetic friction of tires causing deceleration?

It doesn't, unless you brake so hard you skid. If the wheels are in rolling contact then it is static friction. Freewheeling on a level surface, that neither speeds you up nor slows you down.

There is kinetic friction in the axle, creating a torque.

There is rolling resistance between the tyre and the road. This is caused by deformations in each, mostly the tyre.
As the wheel turns, the part coming into contact with the road flattens, as that leaving the road returns to its circular form. The elasticity is imperfect, so the force needed to flatten it is a little greater than that produced by the tyre as it recovers. This means the effective position of the normal force is displaced forwards from the axle, so generates a torque opposing rotation of the wheel.