Do heavier objects fall faster?
- Thread starter Blinkz
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They fall at equal rates, provided that intertial mass = gravitational mass.
This postuilate has never been proven.....though equally, within the limits of experimental accuracy its never been violated....
SO the answer is 'It seems that they fall at the same rate, though its never been proven'
This postuilate has never been proven.....though equally, within the limits of experimental accuracy its never been violated....
SO the answer is 'It seems that they fall at the same rate, though its never been proven'
The general equation of motion of an body is
m.(x double dot) + C.(x dot) + k.x = F(t)
m=mass
C=drag function
k=stiffness
F(t)= Sum of external forces as a function of time
and
I.(theta double dot) + C.(theta dot) + k.(theta) = M(t)
I=mass moment of inertia
C=drag function
k=stiffness
M(t)= Sum of external moments as function of time
Don't normally include the k.x or k.theta unless the body is distorting as it moves. Or something along those lines.
m.(x double dot) + C.(x dot) + k.x = F(t)
m=mass
C=drag function
k=stiffness
F(t)= Sum of external forces as a function of time
and
I.(theta double dot) + C.(theta dot) + k.(theta) = M(t)
I=mass moment of inertia
C=drag function
k=stiffness
M(t)= Sum of external moments as function of time
Don't normally include the k.x or k.theta unless the body is distorting as it moves. Or something along those lines.
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VeNT said:
Hold the phone, you what? So you are saying if I wang a cat out an aeroplane at 10,000 feet it will be fine (aside from my visit from the RSPCA)? I've got to admit to never having done physics and having little to no interest in it but I'm pretty certain that terminal velocity is terminal velocity and cats don't have their own independent version.
terminal velocity is composed from your mass, your density and your shape.semi-pro waster said:
cat = Light + Furry + spreadable.
its quite possible that a very furry and light cat would have a non fatal terminal velocity, but not most cats.
Visage said:
Well, it's Newtonian mechanics, we know it predicts the movement of everyday things pretty well, for 99% of circumstances.
In terms of the model, the rate of the object falling *is* proven to be constant, regardless of the mass, because it's just a mathematical case of the mass of the object cancelling out.
But like I said, it's just a model.
daz said:
But the model is based on an assumption that is unproven.
When one says F = MmG/r^2 and F=ma, and equate the two to get a = MG/r^2 to 'prove' that a is independent of mass (M is the mass of the earth), then the assumtion is that the inertail mass in F=ma is equal to the gravitational mass in F = MmG/r^2.
This hasnt been proven. Within the limits of expiremental accuracy they're the same, but there's no inherent reason why they should be.
daz said:
Rubbish. The idea that we assume equivalence when there is no reason to is bad. There is no non-empirical evidece that inertial mass = gravitational mass.
But anyway, that's basically what I said... It's a model, but it works for everyday circumstances in the most part.
Yes, it works, but that does not mean it is correct.
Visage said:
Sorry, I got ahead of myself, I thought you were talking about a relativistic mass for a second.
"There is no non-empirical evidence that inertial mass = rest mass"? Surely non-empirical evidence is the kind of evidence that we don't want. Empirical evidence suggests that there is exactly no difference between the inertial mass and gravitational mass.
Of course, if there was an experiment performed where they differed, it would shake the foundations of physics, because so many models and theories assume them to be the same. But they haven't found a difference yet, so everything is OK for now.
