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2d
comment Which ball touches the ground first?
It would be nice to add buoyancy too. In air it will be significantly smaller than drag (friction), but it would make the answer more general.
Jun
6
awarded  Critic
Jun
6
comment Why do heavier objects fall faster in air?
@ja72: But the results are answering the question what is the speed after time $t$.
Jun
6
comment Why do heavier objects fall faster in air?
@auxsvr: The result is correct. But it is expressions for $v(t)$ and $lim_{t\to\infty} v(t)$. So the integral should also be expression for $v(t)$, not $t$.
Jun
6
comment Why do heavier objects fall faster in air?
@ja72: I believe that's worse. The left hand was correctly $v(t)$, so the integral must have $t$ as free variable. $m\int_0^t\frac{dt}{mg - cv^2}$.
Jun
6
comment Why do heavier objects fall faster in air?
@auxsvr: I am not sure that was a correction. Velocity is the dependent variable here. The free variable is time, so it indeed should be $0$ to $t$. And the numerator should be $dt$. Because in the "d" notation, the first equation is $m\frac{dv}{dt} = mg - cv^2$ and you "multiply" by $dt$ to integrate.
Jun
6
awarded  Yearling
Jun
6
comment Why do heavier objects fall faster in air?
@auxsvr: Rotating the object won't change the fact that drag always acts in opposite direction from velocity and buoyancy always acts in opposite direction of gravity. So the acceleration will differ, but not the qualitative result.
Jun
6
revised Why do heavier objects fall faster in air?
use proper variables in the expression
Jun
6
suggested suggested edit on Why do heavier objects fall faster in air?
Jun
6
comment Why do heavier objects fall faster in air?
You have not mentioned either drag nor buoyancy, both of which can be easily quantified. And the talk about probability just does not make sense. Probability is not involved; the example in the question is feather and a lead (forged into the same shape) falling in still air from zero velocity compared to the ground and the outcome is perfectly deterministic there.
Jun
6
comment Why do heavier objects fall faster in air?
@Trengot: This answer is correct. The terminal velocity only comes about due to drag, since buoyancy does not increase with speed. You are right that buoyancy has to be included in the question, but for a feather drag is more significant than buoyancy.
Jun
6
comment Why do heavier objects fall faster in air?
@Godparticle: Atmospheric pressure only comes into question by creating buoyancy due to difference of pressure on the top and bottom surface of the object. Since pressure increases with depth, buoyancy always acts upwards. But even for feather buoyancy is still considerably smaller than drag.
Jun
6
comment Why do heavier objects fall faster in air?
@Godparticle: Force is indeed vector quantity. A drag force, that is discussed here, is always opposite direction from the velocity of the object relative to the fluid. So in still air, the drag of falling object is always up. If the air was moving down faster than the object, then the drag force would be directed down and the feather would indeed accelerate faster.
Jun
6
comment Why do heavier objects fall faster in air?
I am joining the downvote. This does not answer the question.
May
11
comment Why doesn't more light bounce off of things in the manner of sound?
Actually diffraction occurs even around edges of larger gaps up to infinite. But it only happens in area around the edge comparable to the wavelength, so for light only very little light is diffracted.
May
11
comment Why doesn't more light bounce off of things in the manner of sound?
Being able to hear is similar to being able to see red and green flashes and be able to tell their length and frequency. It requires only receiving the correct frequency, but no directional resolution. While being able to see requires spatial resolution.
Apr
29
comment Is frequency quantized?
I have not looked at the paper the linked article alludes to, but the article itself misses the key piece of the argument. Namely why would the fact that it is hard to evaluate the model have any effect on whether the modelled system can behave in certain way. Especially since it is already known that quantum calculations allow doing certain operations faster (but with a chance of failure) than calculation on traditional computer.
Apr
24
comment What happens in a car crash?
@CarlWitthoft: Well, it is a problem of both. There are two unknowns, the velocities of the two objects after collision. So you need two equations to solve them. Conservation of momentum provides one. The other depends on how elastic the collision is. In perfectly elastic one, all energy remains as kinetic and conservation of energy is used. In non-elastic one the objects end up with the same velocity and conservation of energy just tells how much energy was released as sound and heat. Real cases are somewhere between these two.
Apr
13
comment Why can light (photons) bends in a curve through space without mass?
@MarkHurd: The observers will see the bend because it is effect of gravity. Whether they are "in" the gravitational field (whatever it means) does not matter.