Investigating Fictitious Forces in Car Acceleration

In summary, the conversation involved a discussion about the behavior of smoke or helium balloons in a moving car, specifically in cases where the acceleration is much greater than the force of gravity. The question was whether gravity can be ignored in these extreme cases, and the answer is no, as the acceleration is still the sum of the two vectors. The topic then shifted to the sensation of being pushed outward in an accelerating frame of reference, and the question was whether this affects the way vectors are added. The final conclusion was that the addition of vectors remains the same in non-inertial frames of reference.
  • #1
Quadrat
62
1
Hi,

I was sitting and thinking of the case where a smoke is rising from say, some incense inside of a car that is accelerating.
I thought that it must act the same way as a helium balloon would have. When you turn left, the smoke tends to go left, when you accelerate in a straight line the smoke goes forward etc.

I was thinking of the extreme cases where the centripetal acceleration or the acceleration in a straight line is much greater than the acceleration due to gravity if one could treat the cases as if there's no component downwards. Am I thinking of this in the wrong way? It might be more complex than just adding the two accelerations to get a resulting acceleration which leads to a centrifugal force and makes the air and smoke react in other ways than if it were inertial. Let's say in the case that the car has a constant acceleration g both forward and downward.
 
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  • #2
Not sure what your question is. Can you ignore gravity as a force if your acceleration is high enough? No.

It's still the sum of the two vectors. even if one is much larger than the other.
 
  • #3
DaveC426913 said:
Not sure what your question is. Can you ignore gravity as a force if your acceleration is high enough? No.

It's still the sum of the two vectors. even if one is much larger than the other.

Take the case where you are on an amusement ride going fast in a circular motion and you're experiencing the centrifugal force. I'm not talking about the philosophical aspects of it. It's not like you really care for or think of the acceleration due to gravity when you are pushed back into your seat immensely. And in the case where the acceleration due to gravity is so small in comparision to the linear or centripetal acceleration that it must be OK to neglect it altogether and think of in which way the smoke or the helium balloon will rise.
 
  • #4
Quadrat said:
Take the case where you are on an amusement ride going fast in a circular motion and you're experiencing the centrifugal force. I'm not talking about the philosophical aspects of it. It's not like you really care for or think of the acceleration due to gravity when you are pushed back into your seat immensely. And in the case where the acceleration due to gravity is so small in comparision to the linear or centripetal acceleration that it must be OK to neglect it altogether and think of in which way the smoke or the helium balloon will rise.

If you were being pushed back into your seat, you would feel a force on your chest. You don't. The force you feel is the seat pushing your back inwards.
 
  • #5
PeroK said:
If you were being pushed back into your seat, you would feel a force on your chest. You don't. The force you feel is the seat pushing your back inwards.

One get's the sensation of being pushed outwards in an accelerating frame of reference however. But I don't get how your reply was helping me answering the actual question.
 
  • #6
Quadrat said:
One get's the sensation of being pushed outwards in an accelerating frame of reference however. But I don't get how your reply was helping me answering the actual question.

Well, I'm sorry to say, I don't really understand either of your posts. Acceleration is a vector, hence you use vector addition when you have multiple accelerations. Where's the confusion?
 
  • #7
PeroK said:
Well, I'm sorry to say, I don't really understand either of your posts. Acceleration is a vector, hence you use vector addition when you have multiple accelerations. Where's the confusion?

Since it's viewed from a non-inertial reference frame I was wondering if it's more complicated than just adding the two vectors or not.
 
  • #8
Quadrat said:
Since it's viewed from a non-inertial reference frame I was wondering if it's more complicated than just adding the two vectors or not.

Why should it be? And, what else would you do? Fictitious forces are still vectors influencing motion in the usual way. The difference is that you don't acually feel them (other than psychologically).
 
  • #9
PeroK said:
Why should it be? And, what else would you do? Fictitious forces are still vectors influencing motion in the usual way. The difference is that you don't acually feel them (other than psychologically).

Sigh. That was why I was asking in the first place. If I had all the answers then I wouldn't be asking any questions - would I?
 
  • #10
Quadrat said:
Sigh. That was why I was asking in the first place. If I had all the answers then I wouldn't be asking any questions - would I?

Your question seems to be: if one vector is much bigger than another, then perhaps you can't just add them together, but do something complex with them instead?

I'm not sure how to answer that.
 
  • #11
Quadrat said:
Sigh. That was why I was asking in the first place. If I had all the answers then I wouldn't be asking any questions - would I?
So, did post #2 answer it?
 
  • #12
Quadrat said:
Since it's viewed from a non-inertial reference frame I was wondering if it's more complicated than just adding the two vectors or not.
Inertial forces were defined such that it's not "more complicated".
 
  • #13
DaveC426913 said:
So, did post #2 answer it?
Yes it did! I wasn't more to it than I imagined. :) The thread was more of a "did I miss something important"?
 

Related to Investigating Fictitious Forces in Car Acceleration

1. What are fictitious forces in car acceleration?

Fictitious forces, also known as inertial forces, are forces that appear to act on an object, but are actually due to the object's acceleration and not caused by any physical interaction with another object. In the context of car acceleration, fictitious forces arise due to the car's acceleration or deceleration.

2. How do fictitious forces affect car acceleration?

Fictitious forces do not actually affect the car's acceleration. They only appear to do so from the perspective of an observer who is not in the same frame of reference as the car. In reality, the car's acceleration is caused by the net force acting on it, such as the engine's power or the force of friction from the road.

3. How can we investigate fictitious forces in car acceleration?

To investigate fictitious forces in car acceleration, we can use the concept of relative motion and frame of reference. This involves analyzing the car's motion from different perspectives and comparing them to understand the role of fictitious forces in the car's acceleration.

4. Are fictitious forces important in understanding car dynamics?

Yes, understanding fictitious forces is crucial in understanding car dynamics. It helps us explain the motion of a car from different perspectives and understand the role of different forces in its acceleration. It also helps us make accurate predictions and calculations for the car's motion.

5. Can fictitious forces be eliminated in car acceleration?

No, fictitious forces cannot be eliminated in car acceleration. They are a result of the car's motion and are necessary to explain and understand its behavior. However, they can be minimized by choosing an appropriate frame of reference that eliminates or reduces the effects of fictitious forces.

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