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When I’m in a car at high speed , I get kind of like pushed back if I’m sitting on the cars seat. How does it happen and why ?

If I’m in a car , then I have the same speed as car and for the car , I am at rest. How is it possible I am getting pushed back which means I have some acceleration. Isn’t it wrong ?

I checked on internet and they it happens only when the car is accelerating. Even though it is accelerating , still , so is the person in the car and therefore , he should not get pushed back.

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  • $\begingroup$ The opposite of when you brake suddenly you get thrown forward; inertia. $\endgroup$
    – Jim Clark
    Commented May 9, 2021 at 16:04
  • $\begingroup$ Now add a helium filled balloon in the car with the windows up. It does the opposite. The balloon moves forward as you depress the accelerator. The air molecules pile-up in the back of the car with positive forward acceleration making the air in the front in the vehicle less dense; thus floating forward. $\endgroup$
    – Jim Clark
    Commented May 9, 2021 at 16:19
  • $\begingroup$ I don't get pushed back in a car at high speed unless it is accelerating. Are you the one driving? If not, it's probably all in your mind or the driver is not taking too much effort to drive at a constant speed. And is the road straight? If it's not, then you may be experiencing centripetal acceleration. $\endgroup$
    – DKNguyen
    Commented May 9, 2021 at 18:25
  • $\begingroup$ Get the person to accelerate at the rate the car accelerates and they won't get pushed back. $\endgroup$
    – StainlessSteelRat
    Commented May 10, 2021 at 0:07

3 Answers 3

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You're not being pushed back. You can do a simple experiment: hang a small weight from your rear-view mirror (or some more convenient spot) with a few inches of string. Note its position with your car parked. You should see it in the same position when moving at a constant speed. Try it on a smooth road. You'll see it swing to the rear when accelerating, and forward while decelerating.

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It is the effect of the "inertia force", which always occurs during the event of "sudden acceleration, or deacceleration", and always in the reversed direction of the acceleration, or deacceleration.

The most obvious examples are standing on a bus or train, facing the direction of driving, you are likely to fall backward when the vehicle suddenly starts to move, and lean forward when the brake is suddenly applied.

In physics, $F = m*a$, and the inertia force is simply $F = -m*a$, which forms the base for many engineering applications, such as earthquake design of structures.

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Actually, when you are accelerating you are not pushed back, instead you are pushed forward.

Initially, you are travelling with the same speed with the car. if the speed is constant then there is no horizontal force. When you hit the gas to accelerate, what happens is that the wheels push forward the car.

The person in the car wants to maintain the kinetic state, but as the car accelerates, the person sinks into the chair (which in turn pushes forward), and as a result the person accelerates with the car.

That sinking feeling is what you describe as "being pushed back".

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