Would you jump or burn?

[Plow]

Mass has a direct effect on the function that will determine the evolution of drag over time, which is what we should be studying here instead of a snap shot at v1=v2.


Drag= Density pf the fluid*velocity*surface area

Velocity is NOT a constant, it's a function of time with mass as parameter somewhere (because f=ma, and a having a direct impact on v(t)).


But terminal velocity IS a function of weight, and since velocity play a direct role when you calculate the drag, object of different weight will have different terminal velocities and therefore, different drag.



[edit]
Saying that mass does not have a direct effect on drag is completelly misleading if you don't mention its effect on velocity.

I can't believe I have to do this for one of the "physics people"...

No matter how much the object weighs, at a given speed and surface area, the drag is exactly the same.

If you want to calculate the speed/acceleration, then yes, you need to know the weight.

If you know the speed and the surface area, then you know the drag, you absolutely do not need the weight.

[Jefe]

Weight (mass) is completely, 100%, in all cases irrelevant in terms of terminal velocity.

Sent from my Samsung Galaxy S 4G using Tapatalk

Sorry fat choco and other dudes:

vt = ((2mg/DρA))^1/2, not only does one's mass count, but also the cross-sectional area. The equation is pretty straight forward, the only obscure variables for a regular Joe would be D: drag coefficient, and rho: air density.

Btw, I thought it was a long chain of troll posts. :U

[Kaylia]

No matter how much the object weighs, at a given speed and surface area, the drag is exactly the same.

Do you even read my post, or you are just pressing quote than spewing bullshit. I've said that in the very first post, and the most that followed.

First two posts (first one wasnt even directed at you to begin with)

If you talk exclusively about the resulting force, then yes, it's in function speed and surface area (basically, how many atoms you hit [and how] per unit of time). However, the variation of speed is determined by the mass, and this will have a direct impact on your speed.

What I'm saying is that your statement is only true if you move at a constant speed, which is a limiting scenario when you want to study the behavior of something that move.

Calculating the drag for a given surface and speed is worthless. You're calculating a force, then do nothing with it when this force has an impact on the evolution of the system in space, and the drag. Like I said 10 times, what you want to know is the function of Drag(time). That's what matter, and mass will come to play here. Calculating the force alone is useless high school material.

[archibaldcrane]

Sorry fat choco and other dudes:

vt = ((2mg/DρA))^1/2, not only does one's mass count, but also the cross-sectional area. The equation is pretty straight forward, the only obscure variables for a regular Joe would be D: drag coefficient, and rho: air density.

Btw, I thought it was a long chain of troll posts. :U

A 10 lb. bowling ball and a 12 lb. bowling ball are dropped from an airplane at the same time. Assuming perfect conditions and the balls being identical other than mass, which one hits the ground first?

Oh gotcha. Because of greater mass, the heavier object has more force, meaning the affect of the same amount of drag (being that the objects have the same surface) slows the heavier one less - or that it will reach terminal velocity at a higher speed. In a vacuum they'd fall at the same speed but with resistance, the greater force (mass*acceleration) of the heavier ball will "cut through" the drag more.

[Plow]

Do you even read my post, or you are just pressing quote than spewing bullshit. I've said that in the very first post, and the most that followed.

First two posts (first one wasnt even directed at you to begin with)



Calculating the drag for a given surface and speed is worthless. You're calculating a force, then do nothing with it when this force has an impact on the evolution of the system in space, and the drag. Like I said 10 times, what you want to know is the function of Drag(time). That's what matter, and mass will come to play here. Calculating the force alone is useless high school material.

Again, what the fuck is your point?

Drag and weight are independent factors. There is no *DIRECT* effect. That's all I've been saying this entire time.

[Plow]

A 10 lb. bowling ball and a 12 lb. bowling ball are dropped from an airplane at the same time. Assuming perfect conditions and the balls being identical other than mass, which one hits the ground first?

Oh gotcha. Because of greater mass, the heavier object has more force, meaning the affect of the same amount of drag (being that the objects have the same surface) slows the heavier one less - or that it will reach terminal velocity at a higher speed. In a vacuum they'd fall at the same speed but with resistance, the greater force (mass*acceleration) of the heavier ball will "cut through" the drag more.

Yeah, the answer is the 12 pound one, provided the distance is far enough for it to exceed the 10 pound one's terminal velocity.

They're going to fall at the exact same rate, and experience the exact same drag, until then.

[Mindfox]

Burn then jump. Live fast, die young, leave a beautiful crater.

[Kaylia]

They're going to fall at the exact same rate, and experience the exact same drag, until then.

Are you retarded?....They won't experience the same drag after the time lapse. This is what I've been saying since the beginning, but it seem to be too hard to grasp.


Let's say that at some point, both object are falling at the same speed and receive the same drag. dv/dt for the heavier object is going to be much smaller (since Fd won't have a huge impact on the total force, and incidently, the acceleration) . This mean that the heavier mass is going to continue falling at high speed, while the smaller one is going to slow down right away. Even if its just 0.0000001 sec, there will be a difference in speed, and a difference in the drag both object will feel.

[Kaylia]

Hell, just look at what happen if you have an object of infinite mass versus one that weight nothing using basic newton shit,

Newton Equation for dummies
Total force = Gravitational force - drag
F = ma or a = F/m

Gravitional force = mass*9.8m/s² (on earth)
Drag = constant given a certain speed, surface and density of the fluid


Object #1: Near infinite mass
Total force = Huge number - d
Acceleration = 9.8m/s² - something incredibly small

Object #2: Incredibly small mass with same drag
Total force = very small number - d
Acceleration = 9.8m/s² - something huge

In the 2nd case, it wouldn't actually start flying, but the drag equation would fall apart, and the object simply wouldnt be heavy enough to push through air molecule



What you're left with is the proof that the heavier object pretty much ignore drag, while the light one are slowed down extremely fast


If you look at how the drag progress over time, you will notice that it keep increasing linearly with the speed for the big object, while it maxes out much faster for the light object.

[Neoscrilla]

I'd jump

[The Stig]

Jump, and then use Heroic Leap at the last second to avoid fall damage!

[pohibaba]

I'd jump out of a building just to get away from these nerds and their physics argument.

[Sqwunk]

Honestly, probably jump, I'm kind of scared of heights but fuck burning to death. Like stated before you're gonna die pretty instantly if you jump.

[Sqwunk]

Also all this physics stuff is irrelevant



Just aim for the bushes bro

[Kaylia]

^
If only the rest of the movie could match that scene.

[Plow]

Hell, just look at what happen if you have an object of infinite mass versus one that weight nothing using basic newton shit,

Newton Equation for dummies
Total force = Gravitational force - drag
F = ma or a = F/m

Gravitional force = mass*9.8m/s² (on earth)
Drag = constant given a certain speed, surface and density of the fluid


Object #1: Near infinite mass
Total force = Huge number - d
Acceleration = 9.8m/s² - something incredibly small

Object #2: Incredibly small mass with same drag
Total force = very small number - d
Acceleration = 9.8m/s² - something huge

In the 2nd case, it wouldn't actually start flying, but the drag equation would fall apart, and the object simply wouldnt be heavy enough to push through air molecule



What you're left with is the proof that the heavier object pretty much ignore drag, while the light one are slowed down extremely fast


If you look at how the drag progress over time, you will notice that it keep increasing linearly with the speed for the big object, while it maxes out much faster for the light object.

right, it will reach a higher terminal velocity...

inertia, though, you seem to have entirely erased from your calculations


am I incorrect in my understanding that the same inertia created by the mass which would allow it to "fight" the wind resistance better would also be affecting its ability to speed up, and fight said resistance in an exactly inverse proportion?

that's how it works with the force of gravity, why would the force of air resistance be different?

[Kaylia]

am I incorrect in my understanding that the same inertia created by the mass which would allow it to "fight" the wind resistance better would also be affecting its ability to speed up, and fight said resistance in an exactly inverse proportion?

that's how it works with the force of gravity, why would the force of air resistance be different?

Your understanding do seem to be incorrect. What is constant for any objects is the " gravitational acceleration", not the gravitational force. That's why everything fall at the same speed when no other force are involved.

I will post a series of statement, tell me where you disagree, and we will start from there.

#1
In this problem, there is only 2 forces applied to both objects. The gravity, and the drag.

F_total= F_grav - F_drag
F_total = mass * acceleration
This acceleration is the one that matter when you want to determine at which speed the item is going to fall.

#2
The gravitational force is not the same for both object. The heavier mass get pulled a lot harder than the smaller one because it need a lot more energy to accelerate at the same speed.

#3
The drag force is the same for both masses initially since they share every characteristic (speed and shape). However, in one case, it's insignificant compared to the gravitational force, while in the other, it is.

#4
The acceleration for both is going to be different because a= (#2-#3)/m.

Example (200kg vs 0.2 kg)
F_total = 2000N - 1N = 200kg*acceleration (heavy object)
F_total= 2N - 1N= 0.2kg*acceleration (light object)

For the heavy object with this drag, it would be close to 9.995m/s². For the light object, it's going to be (5m/s²)


#5
Because they have different acceleration, the smaller mass is going to start falling down much slower than the heavier one. None of them reached the terminal velocity, they just started falling.



What I did with the drag isn't entirely correct, because it's going to be changing constantly as the speed change. To be accurate, I would need a derivative form, but the result would be the same.

inertia, though, you seem to have entirely erased from your calculations

Trust me, I didn't forget inertia. That's how I looked at the problem in the first place to make sure I didn't have it wrong. Like I said in my very first post, it's actually easier to imagine air resistance as a collisions with air particles that have no inertia (it's a gross approximation since it doesn't include fluid behavior, but mechanically, that's what happen).


Every seconds, the Earth is going to give the object more inertia, and part of it will be lost to the collision. Because one object received much more inertia than the other, and both lose the same amount of inertia, one is going to lose a lot more speed than the other.




[edit]

What you're telling me is that both items will free fall at the same speed until they reach a point called "terminal velocity" like this


http://img607.imageshack.us/img607/6223/speede.jpg


You can tell right away it's wrong, because you will only see smooth curves in physics. I mean, just try to calculate the acceleration when it reaches terminal velocities on tihs graph, and you will see it doesn't work.

[Deadgye]

Gravity points down, drag points up. Gravity is constant, but drag is a function of mass and surface area and velocity and etc. If it weighs more it has less drag and thus resists gravity less, and thus falls faster. This isn't that hard people. D:

I'd personally just place some water outside the window and flow down nice and slow. In seriousness though, I'd try my best to fight my way through the fire using some short of make shift breathing apparatus. If I'm going for broke I'm going to show as much skin as possible and try my hand at sliding down the building wall. The coefficient of friction between skin and glass is pretty decent... going to be one hell of an indian burn though.

[Djghost454]

Burn then jump. Live fast, die young, leave a beautiful crater.

http://www.youtube.com/watch?v=y9d_E...tailpage#t=32s