Zero speed due to air resistance

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Discussion Overview

The discussion revolves around the effects of air resistance on the speed of a body, particularly whether a body subjected to air resistance will eventually reach zero speed or if it will slow down indefinitely without reaching that point. The scope includes conceptual reasoning and theoretical implications related to motion and forces.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions whether a body subject to air resistance will eventually reach zero speed or if it will only slow down indefinitely.
  • Another participant seeks clarification on the terminology used and specifically asks if it means the body won't reach zero velocity.
  • A third participant references terminal velocity, explaining that the drag force increases with velocity and that an object under gravity will reach a point where acceleration due to drag balances gravitational acceleration, resulting in zero acceleration but not necessarily zero velocity.
  • One participant argues that while acceleration may reach zero, this does not imply that velocity will also reach zero, especially in cases where there is only initial speed and air resistance acting on the body.
  • Another participant suggests that classically, speed approaches zero asymptotically, but in reality, random thermal motion may dominate at very low speeds, complicating the situation.

Areas of Agreement / Disagreement

Participants express differing views on whether a body will reach zero speed due to air resistance. There is no consensus, as some argue it approaches zero asymptotically while others suggest it may never actually reach zero.

Contextual Notes

The discussion includes assumptions about the nature of air resistance and the conditions under which the body is moving, such as the presence of initial speed and external forces like gravity. The implications of thermal motion at low speeds are also noted but not fully resolved.

DarkFalz
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Hello,

the other day i was playing pool, and i wondered about the following question: when a body is subject to air resistance, does it eventually get to zero speed? Or does it gradually slow down but never reaching 0 speed?

Excuse me if this question is nonsense, but when i heard about another subject, termodynamics, where the temperature of two bodies exchanging temperature never gets totally even, i thought about this situation with regards to speed.

Thanks in advance
 
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Im sorry but

I'm sorry, but i did not understand your answer. I am not used to the terminology you used. Do you mean that, in fact, the body won't reach zero velocity?
 
http://en.wikipedia.org/wiki/Terminal_velocity

The drag force increases with velocity, and if the object is accelerating (e.g under gravity) the velocity is increasing with time. So, after some time the acceleration due to the drag force comes to oppose the acceleration due to gravity; the object reaches zero acceleration, and the velocity can no longer increase- the object is said to have reached terminal velocity.
 
But that

But that only states that acceleration reaches 0, not that velocity will reach 0. In the situation in cause, there is not even an acceleration other than the air resistance, only an initial speed.
 
Classically, I think the speed will approach 0 asymptotically. But in real like, the object will get slow enough that random thermal motion (Brownian motion) will take over.
 

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