What IS Terminal Velocity?

[Kimblair13 0]

OK...so I was having this discussion/argument with my brother...

He says that people fall the same speed bla bla physics and stuff.
I said no, your wrong, fat short person in same body position as tall skinny person will fall faster. Even at terminal.
Then he came up with saying that I must have never been at real terminal cuz they WOULD fall the same. Physics right? He can't be wrong?
So, is our terminal the REAL terminal? Or what? Is he wrong?

[pilotdave 0]

There is no "real" terminal. Terminal is the speed at which your drag equals your weight. Get rid of air resistance and you'll never hit terminal. Change body positions and you change your coefficient of drag so it'll take a different speed to create enough drag to match your weight. Under canopy, you're at a terminal velocity (when you're not maneuvering). Put your canopy into a hard spiral, and it'll eventually reach terminal. Go head down with a slick suit, you'll eventually hit terminal. All those happen at different speeds.

It's also easy to go faster than terminal. Go head down then get back on your belly... you'll slow down because you were faster than terminal. (Drag will be greater than your weight).

Dave

[Lindercles 0]

clicky

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The terminal velocity equation tells us that an object with a large cross-sectional area or a high drag coefficient falls slower than an object with a small area or low drag coefficient. A large flat plate falls slower than a small ball with the same weight. If we have two objects with the same area and drag coefficient, like two identically sized spheres, the lighter object falls slower. This seems to contradict the findings of Galileo that all free falling objects fall at the same rate with equal air resistance. But Galileo's principle only applies in a vacuum, where there is NO air resistance and drag is equal to zero.

it's nasa, which is run by the government, and the government doesn't lie. so it has to be true.

[Kimblair13 0]

YES!
So I'm right and he's wrong.

[polarglitch 0]

i think what your brother meant is this.
in a vacuum, every object falls at the same speed because there is no air resistance. When there is no air resistance, shape does not matter and neither does weight.

In the real world, Shape and Weight matter. A lighter person of surface area, say 1square meter will fall slower than a heavier person of the same surface area. This is weight.
If you consider surface area, lets say you have one person jump horizontally and then vertically later. Because you create more surface area horizontally, more drag is associated, and your maximum speed will be less than if you fall vertically. Thus.. the parachute.

When you come close to losing your life, you learn to value it.
I jumped, I survived, I learnt.

[Kimblair13 0]

No...he was basically saying that we as skydivers never reach the real terminal speed. That we don't get high enough and fall long enough...cuz if we would be at the real terminal speed...everyone would fall the same. He's just full of shit and likes to argue with me.

[Lindercles 0]

so how long does he get to stay with you before he has to go back to the asylum?

[Lindercles 0]

Ok, I can think of two examples that you can use to prove him wrong.

1.) by his logic, if we never reach terminal then we are constantly accelerating from exit to opening. Obviously, we know that we stop accelerating just a few seconds into the skydive.

2.) If we never reach terminal then a person in a head down position could switch to belly and not lose any velocity at all. Which again, we know to be untrue.

Tell him that and then stick out your tongue and go PFPFPFPFPFPFPFP, and maybe even get a little bit of spit on him "by accident"

[skinnyshrek 0]

Well, i am 260 out the door. i cannot fall with someone who is 100 out the door ask him why if we all fall the same speed

http://www.skydivethefarm.com

do you realize that when you critisize people you dont know over the internet, you become part of a growing society of twats? ARE YOU ONE OF THEM?

[happythoughts 0]

Drag and shape matter. Otherwise, you would fall at the same rate with your parachute open as closed. That seems like a bad idea.

[Lindercles 0]

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Otherwise, you would fall at the same rate with your parachute open as closed. That seems like a bad idea.

OOOOOOO, that's a good one! If all objects fall at the same speed, what the hell do we have a parachute for?

Although the mental picture of a person in "freefall" and a person under a canopy hanging out in a vacuum, falling at the same speed is pretty hilarious.

[peckerhead 0]

This is one of the most common asked questions by wuffos.

20 pound bowling ball vs 20 pounds of feathers.

Throw them both off the Empire State building and the bowling ball will win every time.

[Amazon 7]

Show him the Speed Skydiving site... we all have varying terminal velocities by virtue of flying skill and body shape..

http://hangout.no/speednews/

Some of us who compete are going over 300 MPH

[cocheese 0]

In the REAL REAL WORLD:
"Terminal" velocity is the minumum speed required to die from impact from a skydive or swoop.

[kallend 2,026]

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No...he was basically saying that we as skydivers never reach the real terminal speed. That we don't get high enough and fall long enough...cuz if we would be at the real terminal speed...everyone would fall the same. He's just full of shit and likes to argue with me.

Remind him that air density decreases as altitude increases, so terminal velocity is higher at high altitude.

In fact, assuming you keep a constant body position you reach maximum velocity around 10-12 seconds into the skydive and then start slowing down as the air gets "thicker".

...

The only sure way to survive a canopy collision is not to have one.

[Broke 0]

I think the major point he is missing is most "Basic" Physics course neglect the friction of air.

http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html

Divot your source for all things Hillbilly.
Anvil Brother 84
SCR 14192

[godfrog 2]

throw a watermelon out of an airplane and try to catch it and you will have your answer. Don`t do it where the watermelon can hit anything on the ground. lots of velocity there and won`t do any good to what it hits!!!!!

Experience is a difficult teacher, she gives you the test first and the lesson afterward

[SuFantasma 0]

Well, theoretically, everything gravitates towards each other at the same rate of acceleration in a vacuum.

You can explain to your friend that his brain is a vacuum (nothing exists to exert any functional resistance) and therefore in his mind everything falls at the same rate of acceleration.

For any giving system, "terminal velocity" is reached when the acceleration of the object towards the measured target equals zero.

Y yo, pa' vivir con miedo, prefiero morir sonriendo, con el recuerdo vivo".
- Ruben Blades, "Adan Garcia"

[Broke 0]

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Well, theoretically, everything gravitates towards each other at the same rate of acceleration in a vacuum.

You can explain to your friend that his brain is a vacuum (nothing exists to exert any functional resistance) and therefore in his mind everything falls at the same rate of acceleration.

For any giving system, "terminal velocity" is reached when the acceleration of the object towards the measured target equals zero.

only provided that there are no other interfeering gravatational forces.

If you really want to blow his mind just say it is all irrellivant since all matter is comprised of 90% empty space.

Divot your source for all things Hillbilly.
Anvil Brother 84
SCR 14192

[streaker 0]

Not much for book learnin'...but terminal velocity happens every time ya leave the jump ship!

Don't care much if I can beat 20 pounds of feathers as long as I can keep steppin' out of the plane!

Beautiful Landings!


Streaker

Have a yippee ki ya day!

[azureriders 0]

I have had this discussion with more than one physics major who actually understand what is going on. It seems that air resistance affects acceleration but weight does not. however the ratio of weight to air resistance does affect terminal velocity. So therefore if we had two 4in diameter balls, one made of lead and the other of alluminum and both polished to the same smoothness, then they would have the same drag but differ in weight. Let these two balls race from the top of latter they tie, from the top of a tree, still tie, from the top of a sky scraper, hmmm not sure, but from 14000 ft from an otter and they would leave together, stay together until the alluminum reached its terminal, the the lead ball would continue to accelerate to its terminal and therefore win the race.

I am fairly good at math and have saw these formulas worked out and can follow them, but dont ask me to site what they are.

[kallend 2,026]

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I have had this discussion with more than one physics major ...

So therefore if we had two 4in diameter balls, one made of lead and the other of alluminum and both polished to the same smoothness, then they would have the same drag but differ in weight. Let these two balls race from the top of latter they tie, from the top of a tree, still tie, from the top of a sky scraper, hmmm not sure, but from 14000 ft from an otter and they would leave together, stay together until the alluminum reached its terminal, the the lead ball would continue to accelerate to its terminal and therefore win the race.
.

Ummm - wrong in several respects.

...

The only sure way to survive a canopy collision is not to have one.

[Kimblair13 0]

So I told him what everyone here said and he still insists that our terminal velocity is not terminal velocity at all. That there is only ONE true terminal velocity and that is in a vacuum or whatever. He's back home now though, so no more arguing.

[happythoughts 0]

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I have had this discussion with more than one physics major who actually understand what is going on. It seems that air resistance affects acceleration but weight does not.

Umm...no. Some people understand the a+b=c, but cannot properly apply the theoretical to the physical. This sounds like a lot of the people that I took physics with.

Here's a test. I'll loan you my weight belt with 12 lbs in it. Put it under your jump suit so that your shape and external drag do not change. Get your knees in the breeze with that 12 extra lbs and then we'll talk about their theory again.

[Broke 0]

Send him an email to that link I posted, and then call him a jackass. In the real world you cannot neglect the friction of air. If there was no friction there would be no such thing as terminal velocity.

Divot your source for all things Hillbilly.
Anvil Brother 84
SCR 14192