Holy Smoke

Theory and observation..

While I was stopped at a red light and taking a drag on a cigarette a curiosity came over me:

When I accelerate, the smoke that left the end of my cigarette does not travel to the rear of the car. More thinking,  would an un-tethered balloon, stay pace with my accelerating or float to the rear of the car ?

The smoke that leaves the cigarette, although lighter than air, still at a molecular level attached to the cigarette, if so at which point do smoke particles, isolated or collectively, become independent of the cigarette.

What are the factors?

Working trials and experiments.


4 thoughts on “Holy Smoke

  1. Brett

    Before we address the smoke let’s think about something more substantial, like yourself in the driver’s seat. When you accelerate, you are pushed back into your seat by a force.

    In this situation it’s helpful to remember one of Newton’s three laws of motion: F=ma, where “F” is the force that pushes you back into the seat, “m” is your mass, and “a” is the acceleration. The greater your acceleration and the greater your mass, the more force is generated. Since the mass of the smoke is almost nothing, the acceleration multiplied to it will result in an equally negligible force; the smoke won’t move to the back of the car.

    Likewise, how a balloon might be affected will depend on its mass, and of course the resistance of air molecules in the car (though we always ignored air resistance in physics class to keep things simple).

  2. gordy

    While that is all true, the determining factor is if the balloon is untethered, the theory of force may not come into play.

    For example, a balloon filled with helium with just enough weight on it can suspend itself floating in mid air (or nearly suspend itself). If the balloon is located outside the vehicle, and the vehicle accelerates the balloon remains as the vehicle passes by.

    Now, what if that same suspended balloon was placed in the vehicle would it behave the same? Moving to the rear of the vehicle when it accelerates ? The phenomenon of the cigarette smoke is similar. At which point do the particles of smoke become free, (untethered) of the stationary object (end of the cigarette). What if the windows are open ? What happens in a convertible? At which point is enclosure of space affecting the subject? In a test environment wind would need to be eliminated as a factor i.e. a warehouse or hangar.

    I simply must try this!

  3. William

    I think one of the key factors is the air inside the vehicle. This air mass is accelerating along with the vehicle so any local motion (relative to the air mass) of the smoke/balloon will be small.

  4. gordy

    Exactly what I’m suspecting, however there has to be a proportion, ratio of enclosure to air mass density.

Comments are closed.