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United States24691 Posts
On October 23 2008 09:29 travis wrote:Show nested quote +On October 23 2008 09:25 micronesia wrote:On October 23 2008 09:22 travis wrote:
micronesia, what is the role of "drag force" in all of this? The drag force is the force of friction, which is due to air resistance. If there was no air (vacuum) then the objects would fall exactly the same. But since there is air, there is an upward force acting on each of the objects. This opposes the force of gravity, and when this drag force gets big enough, the object achieves terminal velocity. so it comes down to: drag force VS force of gravity and the force of gravity is based upon mass of the objects?
Correct.
edit: but I wouldn't consider that alone a sufficient explanation
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On October 23 2008 09:30 micronesia wrote:Show nested quote +On October 23 2008 09:29 travis wrote:On October 23 2008 09:25 micronesia wrote:On October 23 2008 09:22 travis wrote:
micronesia, what is the role of "drag force" in all of this? The drag force is the force of friction, which is due to air resistance. If there was no air (vacuum) then the objects would fall exactly the same. But since there is air, there is an upward force acting on each of the objects. This opposes the force of gravity, and when this drag force gets big enough, the object achieves terminal velocity. so it comes down to: drag force VS force of gravity and the force of gravity is based upon mass of the objects? Correct. edit: but I wouldn't consider that alone a sufficient explanation
why not?
oh, because of terminal velocity?
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United States24691 Posts
On October 23 2008 09:34 travis wrote:Show nested quote +On October 23 2008 09:30 micronesia wrote:On October 23 2008 09:29 travis wrote:On October 23 2008 09:25 micronesia wrote:On October 23 2008 09:22 travis wrote:
micronesia, what is the role of "drag force" in all of this? The drag force is the force of friction, which is due to air resistance. If there was no air (vacuum) then the objects would fall exactly the same. But since there is air, there is an upward force acting on each of the objects. This opposes the force of gravity, and when this drag force gets big enough, the object achieves terminal velocity. so it comes down to: drag force VS force of gravity and the force of gravity is based upon mass of the objects? Correct. edit: but I wouldn't consider that alone a sufficient explanation why not? oh, because of terminal velocity?
Well I suppose if you just wanted to know which one would have a bigger acceleration, everything else besides mass being equal, then that would be acceptable. If you want to discuss how the objects' motion would change over time, then you'd need to also recognize that the force of friction depends on the speed (in this case)
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On October 23 2008 09:37 micronesia wrote:Show nested quote +On October 23 2008 09:34 travis wrote:On October 23 2008 09:30 micronesia wrote:On October 23 2008 09:29 travis wrote:On October 23 2008 09:25 micronesia wrote:On October 23 2008 09:22 travis wrote:
micronesia, what is the role of "drag force" in all of this? The drag force is the force of friction, which is due to air resistance. If there was no air (vacuum) then the objects would fall exactly the same. But since there is air, there is an upward force acting on each of the objects. This opposes the force of gravity, and when this drag force gets big enough, the object achieves terminal velocity. so it comes down to: drag force VS force of gravity and the force of gravity is based upon mass of the objects? Correct. edit: but I wouldn't consider that alone a sufficient explanation why not? oh, because of terminal velocity? Well I suppose if you just wanted to know which one would have a bigger acceleration, everything else besides mass being equal, then that would be acceptable. If you want to discuss how the objects' motion would change over time, then you'd need to also recognize that the force of friction depends on the speed (in this case)
micronesia,
drag force already accounts for velocity.
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tyvm micronesia, and ty yango and everyone else
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United States24691 Posts
On October 23 2008 09:40 Mooga wrote:Show nested quote +On October 23 2008 09:37 micronesia wrote:On October 23 2008 09:34 travis wrote:On October 23 2008 09:30 micronesia wrote:On October 23 2008 09:29 travis wrote:On October 23 2008 09:25 micronesia wrote:On October 23 2008 09:22 travis wrote:
micronesia, what is the role of "drag force" in all of this? The drag force is the force of friction, which is due to air resistance. If there was no air (vacuum) then the objects would fall exactly the same. But since there is air, there is an upward force acting on each of the objects. This opposes the force of gravity, and when this drag force gets big enough, the object achieves terminal velocity. so it comes down to: drag force VS force of gravity and the force of gravity is based upon mass of the objects? Correct. edit: but I wouldn't consider that alone a sufficient explanation why not? oh, because of terminal velocity? Well I suppose if you just wanted to know which one would have a bigger acceleration, everything else besides mass being equal, then that would be acceptable. If you want to discuss how the objects' motion would change over time, then you'd need to also recognize that the force of friction depends on the speed (in this case) micronesia, drag force already accounts for velocity.
You were going on the assumption that by saying 'drag force' you realize how the drag force works, besides the fact that it is simply a force that opposes motion in a fluid (such as air). I don't believe that was true, however it doesn't need to be given the nature of Travis' request.
BTW Travis who won?
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The other guy won.
So I pay $100, rather than winning $1000.
It's alright, i expected to lose the bet from the start. I assumed I must have been missing something 
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Also the heavier object pulls the earth up toward it more. You wouldn't notice it for any normal thing but it's still there, slightly, and if the thing has the mass of a planet then it becomes important.
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On October 23 2008 10:12 micronesia wrote:Show nested quote +On October 23 2008 09:40 Mooga wrote:On October 23 2008 09:37 micronesia wrote:On October 23 2008 09:34 travis wrote:On October 23 2008 09:30 micronesia wrote:On October 23 2008 09:29 travis wrote:On October 23 2008 09:25 micronesia wrote:On October 23 2008 09:22 travis wrote:
micronesia, what is the role of "drag force" in all of this? The drag force is the force of friction, which is due to air resistance. If there was no air (vacuum) then the objects would fall exactly the same. But since there is air, there is an upward force acting on each of the objects. This opposes the force of gravity, and when this drag force gets big enough, the object achieves terminal velocity. so it comes down to: drag force VS force of gravity and the force of gravity is based upon mass of the objects? Correct. edit: but I wouldn't consider that alone a sufficient explanation why not? oh, because of terminal velocity? Well I suppose if you just wanted to know which one would have a bigger acceleration, everything else besides mass being equal, then that would be acceptable. If you want to discuss how the objects' motion would change over time, then you'd need to also recognize that the force of friction depends on the speed (in this case) micronesia, drag force already accounts for velocity. You were going on the assumption that by saying 'drag force' you realize how the drag force works, besides the fact that it is simply a force that opposes motion in a fluid (such as air). I don't believe that was true, however it doesn't need to be given the nature of Travis' request. BTW Travis who won?
The drag force is a force F (you can double-check this by reducing the units of [check picture]) and this applies at any given time.
![[image loading]](http://upload.wikimedia.org/math/7/6/1/7613c56c8438ae8fa328dcbd4f4f4e7c.png)
where p=density=F(L^-4)(T^2)
u=velocity=L(T^-1)
Cd= dimensionless
A= L^2
Thus, the drag force can be expressed as single force (at any given time).
Edit: Fixed the link to the pic
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United States24691 Posts
On October 23 2008 10:34 Mooga wrote:Show nested quote +On October 23 2008 10:12 micronesia wrote:On October 23 2008 09:40 Mooga wrote:On October 23 2008 09:37 micronesia wrote:On October 23 2008 09:34 travis wrote:On October 23 2008 09:30 micronesia wrote:On October 23 2008 09:29 travis wrote:On October 23 2008 09:25 micronesia wrote:On October 23 2008 09:22 travis wrote:
micronesia, what is the role of "drag force" in all of this? The drag force is the force of friction, which is due to air resistance. If there was no air (vacuum) then the objects would fall exactly the same. But since there is air, there is an upward force acting on each of the objects. This opposes the force of gravity, and when this drag force gets big enough, the object achieves terminal velocity. so it comes down to: drag force VS force of gravity and the force of gravity is based upon mass of the objects? Correct. edit: but I wouldn't consider that alone a sufficient explanation why not? oh, because of terminal velocity? Well I suppose if you just wanted to know which one would have a bigger acceleration, everything else besides mass being equal, then that would be acceptable. If you want to discuss how the objects' motion would change over time, then you'd need to also recognize that the force of friction depends on the speed (in this case) micronesia, drag force already accounts for velocity. You were going on the assumption that by saying 'drag force' you realize how the drag force works, besides the fact that it is simply a force that opposes motion in a fluid (such as air). I don't believe that was true, however it doesn't need to be given the nature of Travis' request. BTW Travis who won? The drag force is a force F (you can double-check this by reducing the units of [check picture]) and this applies at any given time. where p=density=F(L^-4)(T^2) u=velocity=L(T^-1) Cd= dimensionless A= L^2 Thus, the drag force can be expressed as single force (at any given time). Edit: Fixed the link to the pic
I'm not disagreeing with your analysis of what a drag force is (honestly I didn't even read the above). I'm just saying, when Travis refers to the 'drag force', he isn't referring to the specifics, but just to the basics.
edit: oh sorry, I made it sound like you didn't understand it, rather than that Travis didn't. My apologies for the miss-communication.
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Bill307
Canada9103 Posts
On October 23 2008 08:06 travis wrote:
here is my question.
2 objects, same shape, surface, and size. different masses.
both are dropped from an airplane.
before either object reaches terminal velocity, will they accelerate at the same rate?
Their accelerations will be close, but not the same.
The two objects experience different gravity forces and the same air resistance force (at equal speeds).
They have different masses, and whereas the acceleration from gravity is the same, the air resistance force will affect the objects by different amounts because of their different masses.
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