When is Work Done? - P.E., Air Resistance & Gravity

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Discussion Overview

The discussion revolves around the concept of work done by gravity on a particle with potential energy when released, particularly in the context of air resistance. Participants explore how air resistance affects the work done by gravity compared to a scenario without air resistance, touching on factors such as distance, mass, and the nature of forces involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that gravity does a consistent amount of work based on the distance fallen, while air resistance reduces the total work done on the particle.
  • One participant suggests that the work done by gravity can be calculated as 9.8 times the distance, while air resistance contributes negatively to the work done.
  • Another participant questions how air resistance acts, considering whether it is proportional to displacement or velocity, and discusses the inelastic nature of collisions between the particle and air molecules.
  • There is a suggestion that the presence of air resistance leads to a decrease in mechanical energy, which aligns with expectations regarding frictional forces.
  • Participants acknowledge the importance of mass in calculating work done, with one expressing a moment of forgetfulness regarding this factor.

Areas of Agreement / Disagreement

Participants generally agree that air resistance affects the work done by gravity, but multiple competing views remain regarding the specifics of how this interaction occurs and the implications for energy conservation.

Contextual Notes

There are unresolved questions about the exact nature of air resistance and its dependence on various factors, such as velocity and displacement. Additionally, the discussion does not clarify the mathematical relationships fully, leaving some assumptions unaddressed.

pconstantino
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Hello.

If a particle has some P.E. say 100J, when we release it, considering there's air resistance, will gravity do more work than if there was no air resistance?

Thanks
 
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pconstantino said:
Hello.

If a particle has some P.E. say 100J, when we release it, considering there's air resistance, will gravity do more work than if there was no air resistance?

Thanks

What do YOU think? What factors come into play when there's air resistance? And does gravity do work on more than just the particle when there's air resistance?
 
i think gavity does 9.8 * distance of work, and air resistance does -X * distance of work, which at the end decreases the total energy of the particle, is that right?
 
Heh ... my work is *never* done. :-p
 
oh come on... let me go back to my books then.
 
Yup, if the distance doesn't change, the work done by gravity is the same (you did forget the factor m). The fact that the drag makes the total work done over a certain distance less was to be expected, as the mechanical energy (potential + kinetic) is known to decrease in the presence of friction.
 
omg i forgot the mass lol, sorry. thanks mr vodka :P
 
how is the force due to air resistance acting?? (like in general proportional to displacement or velocity of the particle (instantaneous)) and yes..is the collision between the particle and the air molecules is inelastic?? if so then the mass of the aprticle is increased in due course of time...??
hm.., but in general if u wud like answer the question then, the answer is "yes" for same distances in 2 cases ie., ( i) with air friction..2)without air friction)
 

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