Is acceleration still equal in the presence of air resistance?

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Discussion Overview

The discussion revolves around the effects of air resistance on the acceleration of falling objects, particularly comparing heavier and lighter objects. Participants explore the implications of air resistance on terminal velocity and the dynamics of objects like balloons and planes in various conditions, including the absence of air resistance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants recall being taught that heavier objects fall at the same rate as lighter ones in a vacuum, but question this in the context of air resistance.
  • It is noted that heavier objects tend to have a higher terminal velocity due to greater gravitational force, which balances with air resistance at a higher speed.
  • Participants discuss how air resistance scales with velocity, and that lighter objects reach terminal velocity more quickly than heavier ones.
  • There is a mention of an overloaded plane's inability to fly, attributed to the relationship between lift, drag, and weight.
  • Questions arise about why identical balloons fall at different speeds, leading to discussions about the forces acting on them and the nature of air resistance.
  • Some participants assert that for two objects to fall at the same rate, air resistance must be absent, while others argue that the forces of air resistance acting on each balloon are not identical due to their differing weights.
  • There are references to experiments and demonstrations that illustrate these concepts, including anecdotal experiences from participants.

Areas of Agreement / Disagreement

Participants generally agree that air resistance affects the falling speed of objects, but there is no consensus on the specifics of how identical objects can fall at different rates or the implications of these observations. Multiple competing views remain regarding the role of air resistance and the conditions under which objects fall.

Contextual Notes

Participants highlight the importance of considering all forces acting on an object, particularly in the presence of air resistance, which complicates the straightforward application of gravitational acceleration principles.

  • #31
Yes M and m are factors, of course. Makes perfect sense and a bit of a duh moment there.

I was also heading where hmmm27 went in thinking about $$F={m}{a}$$ (or g instead of a if you want to be technical, sure o0)) to describe why without another force (air resistance) acceleration would be equal*. Doubling mass doubles force, yet that yields no change in acceleration: $$a=\frac{F}{m}$$

And of course this is essentially what A.T. said in post #14:
A.T. said:
Things fall the same way if the net force (sum of all forces) is proportional to mass:
- Gravity alone is proportional to mass.
- The sum of gravity and air resistance (which is independent of mass) is not proportional to mass.
*perhaps there's a question still remaining (for me, and perhaps others): is acceleration still equal in the presence of air-resistance up to the point of terminal velocity? Or does air resistance, being an opposing force to gravity, reduce acceleration slightly right 'from the get-go'?

It seems to me that we would then be discussing force subtraction, so relative magnitudes do matter. I.e. the heavier object has, for example, a downward force of 10, the lighter object 5, and the upward (resistive force due to air) is 2 at a given velocity (who cares about units?). For the heavier object, the net downward force is 10-2=8 (80% of the gravitational force). For the smaller object: 5-2=3 (60% of the gravitational force). Thus the smaller object's net force is further reduced proportional to mass at a given velocity.
Wrong, right, confused?
 
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