Would you jump or burn?

[Gredival]

Please, tell me you were trolling...

I said "fall" faster, not accelerate faster. This is a terminal velocity problem, not an acceleration problem. I said accelerating independently. That doesn't mean acceleration at a different rate. It means that they are separate objects which obtain their own independent velocities.

That velocity will be different, REGARDLESS of the equal rate acceleration. We're not working in a vacuum here. Yes in the airless tube, the feather falls the same as the bowling ball. But in the real world that doesn't happen? Why? Air resistance. Air resistance is affected by weight/mass.

A falling object accelerates to higher speeds until they reach terminal velocity where air resistance is equal to their weight. A giant slab of concrete would weigh more than a jumper, and would therefore experience a greater force of gravity and accelerate to higher speeds before reaching a terminal velocity. Thus, more massive objects fall faster than less massive objects because they are acted upon by a larger force of gravity and accelerate to higher speeds until the air resistance force equals the gravity force.

We could also squabble about surface area and how that effects air resistance, but generally this holds true. You would need extreme dimensions to override the effect of mass.

[Kaylia]

So what you are saying is to bring 3 chairs, then slow your fall down a bit on the first, get on the second, do the same, then jump off the third before you hit the ground?

Got it.

Yes, you would have to do it gradually to avoid a drastic change of momentum, but let's say you managed to slow your fall on the first chair considerably, the other chairs around are going to fall much faster than you. You won't be able to get a decent change of momentum on them.

To some extent. I have used the method on ladders a couple times, no higher than a story and a half. I was always taught by my boss, if the ladders falls, ride it to the bottom and then jump. It worked for me twice.

It's not the same here because a ladder isn't "free falling" (it does a circular motion). So yes, holding to the ladder is smarter than jumping off in this scenario.

Of course, this is assuming you get a clean landing in both case, because your legs is going to take the shock a lot better than your head.

[Plow]

Air resistance is affected by weight/mass.

no, it's not

you should stop, you're way, way wrong

Yes, a larger heavier object would make it easier to "jump" from it and not just move it down faster by extending your legs. Jumping on the ground works so well because the ground completely resists the downward pressure so it helps you springboard up. Jumping in midair like this, some pressure will be redirected to basically kicking the object down. The less mass the object you are riding on has, the less resistance you get, so the more you will kick the object vs. jump.

But the main issue is grip/contact. Separate objects tend to drift apart in free fall because they accelerate independently and heavier objects will fall faster. So you have to hold onto whatever it is, and the second you let go you will start to drift apart unless it's exactly the same weight/drag as you. That is primarily what would make it really difficult to truly jump in the sense of fully pushing off something.

And again the impossibility part comes in because you need to jump high enough/hard enough to offset your fall speed. If you're going down at 60mph, you basically need to jump up at 60mph so that at your peak you acquire a total velocity of 0 and you reset your fall speed. Well you don't need to TOTALLY offset your fall speed, just get it to survivable levels. But I highly doubt anyone can generate that much lift in a compromised jump.

Yeah, all that really matters is the end. The rest you could potentially work out (stand on the roof, jump before it lands when it falls), but no matter what, you're not outjumping a thousand foot near free fall.

[Gredival]

no, it's not

you should stop, you're way, way wrong.

For lack of a better source I can find on the internet...

http://en.wikipedia.org/wiki/Terminal_velocity

A free-falling object achieves its terminal velocity when the downward force of gravity (Fg) equals the upward force of drag (Fd). This causes the net force on the object to be zero, resulting in an acceleration of zero.[1]

As the object accelerates (usually downwards due to gravity), the drag force acting on the object increases, causing the acceleration to decrease. At a particular speed, the drag force produced will equal the object's weight (mg). At this point the object ceases to accelerate altogether and continues falling at a constant speed called terminal velocity (also called settling velocity). Terminal velocity varies directly with the ratio of weight to drag. More drag means a lower terminal velocity, while increased weight means a higher terminal velocity.

I understand drag as air resistance.

[Qalbert]

Air resistance has nothing to do with mass, and everything to do with surface area.

[Gredival]

Okay I see, I was imprecise in that sentence.

However my main point remains. Terminal velocity is different from acceleration. Even though objects accelerate at the same rate, they fall at different velocities because their terminal velocity is determined by measuring drag/air resistance (as determined by surface area) against weight.

So yes, object in free fall will separate, accelerating independently to individual terminal velocities. And generally speaking, something heavier will fall faster.

[Plow]

For lack of a better source I can find on the internet...

http://en.wikipedia.org/wiki/Terminal_velocity



I understand drag as air resistance.

increased drag or lowered weight lowers terminal velocity

decreased drag or increased weight raises terminal velocity

drag and weight do not affect each other in any way, shape, or form

[archibaldcrane]

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

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[Kaylia]

Air resistance has nothing to do with mass, and everything to do with surface area.

Fundamentally, mass is still a determining factor.

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.

Air resistance is the collision between multiples bodies (a big object colliding with very light atoms). If both object are going at the same speed, the heavier one will have much more momentum, and can take a lot more atoms before slowing down. In this case, gravity give much more momentum to an heavier object, and because of this, it will take a lot more atoms to slow it down.

Surface area come to play when you want to calculate the fluid dynamics around the object, which is ultimately very important to consider when you're dealing with a gaz or liquid.

[Plow]

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

Sent from my Samsung Galaxy S 4G using Tapatalk

seeing how terminal velocity is the point at which gravity (i.e. weight) = drag, gonna go with no

That's what an engineer would say, but fundamentally, mass is still a determining factor in most case.

If you talk exclusively about the resulting force, then yes, it's in function of the speed and surface area. However, the speed itself is still determined by the mass.

Air resistance is the collision between multiples bodies (a big object colliding with very light atoms). If both object are going at the same speed, the heavier one will have much more momentum, and can take a lot more atoms before slowing down.

Surface area come to play when you want to calculate fluid dynamics around the object, which is ultimately very important to consider when you're dealing with a gaz or liquid, but you can't just dismiss mass.

again, it affects its terminal velocity, it does not actually affect drag

[Thunder]

Anyone have any cool sources/information about absurd distances fallen without parachutes and surviving?

Did some quick and dirty research on google since I've heard of these stories and it seems like a typical 170lb man would reach terminal velocity aat 1,500 feet and be traveling at 120 mph. This is assuming a typical parachuter's stance I think(ie, hands/legs outstretched and falling belly-first so to speak). I guess you can safely say that falling from ~2,000ft and surviving is the same as 20,000ft.

There are stories of a soldier jumping from burning aircraft w/o parachutes at 18,000 feet landing into snow/tree/bushes, aircraft stewardess falling 33,000 feet into snow, and some others in this reading I was linked to from two other websites: http://www.greenharbor.com/fffolder/carkeet.html. And personally, I remember watching a history channel thing on tornadoes and some teenager survived being tossed around his town because he passed out inside and he was thrown(don't remember the actual distance he went, but it was a pretty considerable displacement) while limp so he landed on the ground, face-up, with his arms/legs/back/head(which I've read should kill you - back of the head is worse than front) hitting at roughly the same time.

Coolest thing I read was

the parachutist's "five-point landing" is useful to remember even in the absence of a parachute. Meet the ground with your feet together, and fall sideways in such a way that five parts of your body successively absorb the shock, equally and in this order: feet, calf, thigh, buttock, and shoulder. 120 divided by 5 = 24. Not bad! 24 mph is only a bit faster than the speed at which experienced parachutists land. There will be some bruising and breakage but no loss of consciousness to delay your press conference.

[Plow]

33k would be pretty amazing for an unprotected stewardess, there's a lot of ways to die aside from just impact from that height

[Kaylia]

again, it affects its terminal velocity, it does not actually affect drag

Any change to velocity is going to be affected by the mass of the object that is moving, not just terminal velocity.

Since the speed of the object is a determining factor when you calculate the drag, I simply said you can't dismiss the mass of the object as speed is determined by acceleration, and acceleration will varies for different mass.

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.

[Hyan]

the parachutist's "five-point landing" is useful to remember even in the absence of a parachute. Meet the ground with your feet together, and fall sideways in such a way that five parts of your body successively absorb the shock, equally and in this order: feet, calf, thigh, buttock, and shoulder. 120 divided by 5 = 24. Not bad! 24 mph is only a bit faster than the speed at which experienced parachutists land. There will be some bruising and breakage but no loss of consciousness to delay your press conference.

So what, you can land on a rock almost unscathed if you do this amazing trick?

[Plow]

Any change to velocity is going to be affected by the mass of the object that is moving, not just terminal velocity.

Since the speed of the object is a determining factor when you calculate the drag, I simply said you can't dismiss the mass of the object as speed is determined by acceleration, and acceleration will varies for different mass.

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 something that move .

Speed isn't really "determined" by acceleration, acceleration is just a measure of change in speed...

[Kaylia]

Speed isn't really "determined" by acceleration, acceleration is just a measure of change in speed...

Do you not grasp the concept of time dependant equation?

And if you're seriously insisting on that wording, you're missing the point again.

[Aksannyi]

How did I know before I even read this thread that this hypothetical question would turn into an argument on physics...

[Plow]

I honestly don't even know what you're going on about at this point, but weight does not have a direct effect on drag.

And, since we're talking about a height at which you're going to reach terminal velocity, and potentially higher, the acceleration is a null point.

[Kaylia]

I honestly don't even know what you're going on about at this point, but weight does not have a direct effect on drag.

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)).

And, since we're talking about a height at which you're going to reach terminal velocity, and potentially higher, the acceleration is a null point

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.

[Zubuis]

I'd burn, I hate heights