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Originally posted by Kirkules:

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Originally posted by chrisisall:

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Originally posted by Kirkules:
Just a correction on the aerodynamic(Drag) side of the equation. The total drag on the puppy is the sum of the pressure drag and the skin friction drag. Neither of these is dependent on the mass or density of the puppy. For pressure drag what matters is the cross sectional area of the puppy, for friction drag it's the total surface area. Because the surface area and cross sectional area would be approximately the same for a stuffed animal or a real puppy, the drag coefficient can be assumed to be the same for both.

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But isn't the drag's effect changed by the weight of the object? I mean, doesn't a heavier object need a greater surface area to be affected by drag similarly to a lighter object?

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First thing is that you need to do is separate the concept of weight from that of mass. Mass is independent of Earths gravitational field and is what is most often used in physics. Weight comes from the fact that all mass on Earth is effected by the earths gravity. If you drop an acorn or a feather in a vacuum on the earths surface both will accelerate towards the center of the Earth at 9.81 m/s2. Just like Galileo dropping two steel balls of different mass from the Leaning Tower of Pisa, both hit the ground at the same time. It's a good thing he used balls with enough mass and similar surface areas, making the aerodynamic drag on them an insignificant factor or he would have gotten a different result.

Drag is completely independent of weight or mass. The only other factors that effect drag in subsonic air flow are the density and viscosity of the air, but in this case that too would be the same for both puppies.

I think your mention of surface area is related to your understanding of the aerodynamics of aircraft creating lift with an airfoil. In this case the idea is to maximize lift by having as much surface area as is required to lift the aircraft but at the same time minimize the parasite drag that is a result of the creating lift.

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Originally posted by avengingwatcher:
O2B, you are really coming off as pretentious and this is coming from someone who isn't good with people and completely in love with himself. Hard to argue facts if people don't like you.

When there are no heroes where will we turn?

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Originally posted by out2theblack:

Parasite drag would be stuff stuck on the outside of the aircraft , that creates drag...

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Originally posted by avengingwatcher:
the solider has admitted that he threw a dog, seems to not be much aof a reason to argue this point anymore.

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Originally posted by Kirkules:

Drag is completely independent of weight or mass. The only other factors that effect drag in subsonic air flow are the density and viscosity of the air, but in this case that too would be the same for both puppies.

I think your mention of surface area is related to your understanding of the aerodynamics of aircraft creating lift with an airfoil.

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Sadly, I don't recall seeing the plo slow down as much as I'd expect of a low density object. I wasn't watching for that, so I'm not sure.

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Just watched it three more times, it sure didn't fall as fast as I'd expect it to, plus a bit more of a bounce than the 'splat' I'd also expect.

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Okay, but two things: I feel that it weighed maybe 1/3 to 1/2 of a real puppy's weight, which would account for the rotational inertia, HOWEVER, I've seen cats in mid air extending their legs and ( please excuse my lack of technical language here) 'disrupting the single-axis spin'. The plo spun on a clear single axis, and moved no appendage even once. Once again, I'm left with the phony-puppy assumption.

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Originally posted by Kirkules:
Just a correction on the aerodynamic(Drag) side of the equation. The total drag on the puppy is the sum of the pressure drag and the skin friction drag. Neither of these is dependent on the mass or density of the puppy.

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Another issue is the flight path of the puppy. This is primarily determined by the vertical component of velocity imparted to the puppy when it is released and doesn't tell us much. The only significant factor here is the horizontal distance, since all projectiles essentially fly in a parabolic curve.

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The velocity of the puppy when it leaves the soldiers hand as previously mentioned is governed by the basic equation F=m*a(force equals mass x acceleration). Acceleration is defined as the change in velocity with respect to time as given by the equation a=dv/dt where dv in the change in velocity and dt is the time interval that the force F in applied. Combining these equations we can get the form F/m=dv/dt or dv=(F/m)dt. From this we see that the velocity of the puppy is determined by the force F of the soldiers hand, the mass of the puppy, and the amount of time the force is applied.

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The problem we have here is the one Cantakesky eluded to earlier. Without knowing the mass of the puppy/fake puppy, and the force, and time applied, we can't really determine anything helpful using the laws of physics.

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Originally posted by mal4prez:

Which is different from torque, which is maybe what you mean.
Cats and dogs do this, whipping their tails around to use torque to right themselves. But I don't think this applies applies to the plo problem.

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What is it you figure me to be pretending ?

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Originally posted by canttakesky:

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What is it you figure me to be pretending ?

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Pretentious means, "characterized by assumption of dignity or importance" or "creating an appearance of (often undeserved) importance or distinction."

You create this impression when you patronize Chris. Patronize means, "to behave in an offensively condescending manner." Your comments to Chris are condescending, even if veiled in a compliment.

Just quit it with the "oh.. it's so good you're finally learning...." type comments, and your image of pretentiousness will fade.

P.S. Of course, by giving this advice, I am exuding the same condescension and pretentiousness that I am ascribing to you. My advice implies that I am in a position to lecture you, that somehow I am more socially skilled and less of an ass than you are, which is probably not true.

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Originally posted by out2theblack:
Plus the stray dogs , and the passers-by who want to jump in and gang-rape us to death...

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Originally posted by canttakesky:
Your comments to Chris are condescending, even if veiled in a compliment.

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Originally posted by chrisisall:

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Originally posted by canttakesky:
Your comments to Chris are condescending, even if veiled in a compliment.

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Ahhh, it's his way.

Is that better than a plan?

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Originally posted by chrisisall:

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Originally posted by Kirkules:

Drag is completely independent of weight or mass. The only other factors that effect drag in subsonic air flow are the density and viscosity of the air, but in this case that too would be the same for both puppies.

I think your mention of surface area is related to your understanding of the aerodynamics of aircraft creating lift with an airfoil.

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I mean if you drop a pie tin & an aluminum spoon, both of equal mass, the spoon should hit the ground first due to less 'wind resistance', am I right?

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Originally posted by mal4prez:
Ooooh... I just love me some physics chat! I'm not even kidding. I'm a pig in shit, even with the morbid subject. ]

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Originally posted by Kirkules:
Just a correction on the aerodynamic(Drag) side of the equation. The total drag on the puppy is the sum of the pressure drag and the skin friction drag. Neither of these is dependent on the mass or density of the puppy.

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OK, but drag is a force and it acts on a mass according to F=ma. a, the acceleration, is how we work out the effect of the force on the object's flight path. Since a=F/m, if F is small and m is large, a is very small. No obvious effect on the path.

This is true no matter how we calculate F. Air drag does depend on surface area and velocity and the properties of the air - and not the mass - and you can work the details of that out in all the detail you want, but in the end all that matters is the size of F in relation to m.

Which is why a rock and styrofoam peanut of exactly the same size and shape fall through air at different speeds. The same force is pushing on them both, but the lighter one is easier to move.

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Originally posted by SimonWho:
It's been revealed that the Marine (Charlie) also commited a similar act with his childhood pet.

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Originally posted by Kirkules:

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Originally posted by mal4prez:
Ooooh... I just love me some physics chat! I'm not even kidding. I'm a pig in shit, even with the morbid subject.

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We are strange ones.

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Are there any PHDs in physic out here that can help me out.

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Originally posted by mal4prez:


So, anyhow, the equal and opposite reaction thing... the reaction can be a force, but it doesn't have to be. The force of gravity on my body is equalled by the force of this chair pushing up, but if there's no chair the reaction to the force of gravity will be me falling.

So, a general way to solve mechanics problems (mechanics - forces acting on masses) is to sum up all the forces, and any that are unbalanced make the mass move according to F=ma. Air drag on a projectile is unbalanced - it can't have an equal and opposite force, because the projectile has nothing to push against, like I have the chair and the chair has the floor.

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