davepl

Would it still complete a quarter mile faster than a Z?

If you let a Demon fall from an airplane from a height of exactly 1/4 mile (and ignoring wind resistance), how long would it take to complete the quarter mile, and would it still be faster than the Z?

My guess is right around 9.1 seconds (s = 1/2at^2), but I'm not a math geek. I assumed acceleration is 9.8 m/sec and that the quarter mile is 402 meters.

I think it'd be cool to run a sub-9.1, then, faster than falling!

JerryU

^^^

Yep, 9.06 seconds, Considering you rounded you were right. Would be fun but that sudden stop, not so much!

Now a AA/Fuel dragster does it much quicker because it achieves much more than 1 "g" acceleration.

davepl

Indeed, though I doubt a piston-powered, wheel driven car is very linear... probably launches at 3-4G and goes through the traps well under 1G, as a total guess.

A jet car might be more linear!

village idiot

Thrust is going to increase dramatically as airspeed increases.

Anyway, the car falling from an airplane would have a lot of drag.

JerryU

^^^
More like 8 "gs" off the line and an average of 4 "gs" for the quarter. Just before the traps expect 10,000 hp and looking at the tires at super slomo may well be still over a "g."

NSC5

Your calculated time for dropping from an airplane will be more accurate if you first melt the Demon into a spherical shape

bbrown450

" (s = 1/2at^2), but I'm not a math geek" .....hate to see some math of someone who is !! did not get these in my "Three R's" in school

owc6

Even if you ignored wind resistance, which you can't, you have to factor in forward speed of the aircraft.

Any aircraft large enough to ferry the Demon to altitude would be going in excess of 100 mph on jump run. All that forward speed has to transfer into vertical speed, which makes the trajectory an arc, thus it has longer to travel than only 1/4 mile. And how close to terminal velocity would it get by the time it hit the ground? Even a hovering helo would alter the math because of the downforce of the wind generated.

I certainly don't have the math to figure it out, but I do know how things behave in free fall.

Maybe if it was pushed off a cliff (or platform) that was 1/4 mi. high in a vacuum?

village idiot

Kinda depends. In basic drag free theory, if it comes out of the plane parallel/tangent to the ground, it wouldn't have any bearing.
There's a whole clusterfuck of lift/drag stuff to consider though.

desmophile

The time for the Demon to do the "vertical quarter mile" would be the same independent of the speed of the airplane it was dropped from. The component of horizontal speed would be added to the vertical acceleration and the path of the demon would be curve rather than straight down. At the point of impact, the total speed would be greater, but the vertical velocity would be the same. I think. But I learned long ago not to believe everything I think

Apocolips

Not necessarily true. Even a Blackhawk helicopter could easily lift a Demon to that altitude (about 1330' AGL) without breaking a sweat. Even hover there momentarily, depending on conditions.

drs

Exactly. Horizontal velocity does not factor into the time it takes for an object to reach the ground. A bullet fired from a rifle, and a bullet dropped from the same height as the rifle, will take exactly the same amount of time to hit the ground.

davepl

Except the surface of the earth "curves away" from you, so the horizontal component actually would make a little difference. If your horizontal component were 400m, for example, your vertical distance would increase by however much the earth curves over the span of 400m...

Apocolips

Wait, are you saying that a 7.62mm rifle, fired straight down from an altitude of say 1330’, and a bullet of the same size dropped at the same time would hit the ground at the same time???

drs

Ha. Of course not. That's why I used the phrase "horizontal velocity". Gravity is a constant and doesn't change with the an object's speed. A bullet fired horizontally from a rifle at let's say 10', and a bullet dropped vertically from 10' at the same time as the rifle is fired, will both hit the ground at the same time.

chefcg1

I think this should be a test for the next season of "Grand tour".

KWC6

Depends if it is auto or manual. 😜

davepl

I think they hit the ground at the same time, excepting for the curvature of the Earth as a factor.

It's the old "If a monkey is hanging from a tree and you fire a shot at the exact time it lets go, you still hit it because the monkey falls at the same rate as the bullet" problem.

The one factor I can't account for in my head is the gyroscopic force. There's some resistance to the bullet nosing over, and it can "steal" energy from the bullet's rotation. But that just prevents the bullet from changing angles, and doesn't affect it's drop, so maybe it's not a factor at all.

Remember too, the original post said "ignoring wind resistance" because it gets too complicated with drag. But it doesn't matter for the bullet drop version.

JerryU

The OP did say ignoring air resistance in his question. If not we would have to calculate the terminal velocity and speed reduction with time. And agree would need to estimate the rate of tumble etc if we didn't consider it a sphere!

However since air flow is now done with modeling it could probably be done!

bearphoto

I'd much rather prefer to put it on a road track and watch it through my rear view mirror.