Freefall to sea level

How long would it take to fall from different levels of the atmosphere to sea level at freefall speed?  (80 km, 600 km, and 800 km) 

42

"With air friction acting upon an object that has been dropped the object will eventually reach terminal velocity (around 120 miles/hour for a human body flying in the belly-down arched position; terminal velocity depends on many factors including mass, drag coefficient, and relative surface area) if the fall is from sufficient altitude (2,000 ft) and also otherwise uninterrupted."


to calculate it accurately you would need to know the drag coefficient of whatever was falling, and take into account the differences in air density over the fall, and im assuming you mean an average human.  if you want a really rough estimate, just divide the distance by 120mph or 193km/h depending on your units.  it will be a little longer than that time.

http://bpesoft.com/s/wleizero/xhac/ff1.cgi?h=800000

You need to know the rate of change of air pressure, gravity. Aswell as estimate the size of the vortex created behind the object etc etc..

| , gravity. change

What the fuck lol? The change in gravity is so minor that it's insane to even CONSIDER the change. 9.6 bitch, do you know it.

>9.6

Fails. It's -9.80 m/s^2.

>>6
SPOILER: It's different at 800km from the surface:
http://www.google.com/search?q=G+%2A+mass+of+earth+%2F+%28radius+of+earth+%2B+800km%29%5E2

>>7
FAILS bitch. It's 9.6 at the equator. gb/2/elemtary physics

>>8
not diffrent enough to fucking matter

>>9
It's 9.8. Stop failing. Furthermore, you think 7.7 is "not different enough" from 9.8 to matter? What?

>>10
It's 9.81.

>>11
No, it's 9.806! (This could go on for a while)

>>10


it's not bitch..

learn2terminal velocity. From the distance he's talking about you would hit terminal velocity.

Gb2/fagging/b/

>>10


80 km, 600 km, and 800 km)
80 km, 600 km, and 800 km)
80 km, 600 km, and 800 km)
80 km, 600 km, and 800 km)
80 km, 600 km, and 800 km)
80 km, 600 km, and 800 km)
80 km, 600 km, and 800 km)


SEEMS WE HAVE SOME AMATURE SCIENTISTS IN THIS THREAD.

REFRESHER.


TERMINAL VELOCITY OF A HUMAN BEING FALLING STRAIGHT DOWN IN THE BELLY-DOWN POSITION IS ABOUT 125 MPH. 2.2 KM/H = ~~~~~~~260KM/H
WHICH IS SURVIVABLE IF YOU ARN'T SOME PUSSY BITCH.

AT 80KM'S YOU'RE GOING TO HIT THIS FUCKING TERMINAL VELOCITY AT AVERAGE 9.8~MS^2

FUCKING IDIOTS

AT 80KM'S YOU'RE GOING TO HIT THIS FUCKING TERMINAL VELOCITY AT AVERAGE 9.8~MS^2

WAT U SAY?

>>13
He'll hit terminal velocity when dropping at 7.7m/s^2 after a longer period of time than he would if he was dropping at 9.8m/s^2. Jesus Christ you're a fucking idiot.

TERMINUAL VELOCITY = 1/0

>>17
oh shi-

you will actually never reach terminal velocity. as time goes to infinity, the velocity approached terminal velocity. but usually it's like an asymptote.

v(t) = sqrt(mg/b) * tanh[t / sqrt(m*g/b)]

time at terminal velocity would be:

v_terminnal = sqrt(m*g/b) = sqrt(m*g/b) * tanh[t / sqrt(m*g/b)]

=> 1 = tanh(t / sqrt(m*g/b)

=> atanh(1) = t / sqrt(m*g/b)

=> t = atanh(1) * sqrt(m*g/b)

inverse hyperbolic tan (atanh) of 1 is infinity. so you never really reach terminal velocity, just gets really really close to it, so the difference doesn't really matter.

>>19
disagree,
if you changed your body position such that you passed terminal velocity in a belly down position, you would then, upon returning to belly-down position, be decelerating back to the point you had previously reached.

What the fuck? How is this thread filled with so much fail? Most of the matter in the atmosphere is in the first 10 km or so, and the atmosphere is so thin past 120 km that it has no effect on orbiting bodies. The international space station orbits at 360 km; obviously you're not going to get any atmospheric drag.

At 800 km above the surface, you're going to fall for roughly 700 km without any air resistance whatsoever (i.e. NO TERMINAL VELOCITY YOU MORONS) acheiving a speed of about 3500 m/s (8000 mph) before you even notice any atmospheric drag. At which point you would vaporize. GG.

If you want an answer to your question >>1, get a curve of atmospheric density versus altitude, then write a differential equation relating the differential of distance to the differential of time based on current speed and altitude using the equations of atmospheric drag and gravitational acceleration, then integrate it numerically. Piece of cake.

>>20
But you cheated okay.

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>>7


Fails harder, it changes based on your position and year.  I say year because really old phys textbooks will actually just round it to ten because you can still teach the basic physics and not have to worry about decimal calculations in an age where calculators didn't exist :)

As for position, it could be 9.6 in magnitude depending on where you are.  it can even vary by +-.1 just on where YOU ARE ON THE EARTH  because the Earth itself isn't a perfect sphere but more of a spheroid

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I would calculate my Body Mass Index first. Only then will I determine the true speed of my body. On my healthy days I will generally fall faster than my fat days. Although terminal velocity may have some significance, but the real factor of speed lies in your BMI. I should know, I've bungy jumped before.