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Pomonian t1_j8omppy wrote

Reply to comment by ShatterStorm76 in Tortoise vs Hare by toonhole

Bullet. What goes up, must come down.

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GodzlIIa t1_j8or3es wrote

Apparently they live in a vacuum

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upvoatsforall t1_j8p4iqi wrote

And not on a rotating planet with a Coriolis effect.

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GodzlIIa t1_j8p5h8m wrote

Does Coriolis effect work on things shot straight up? I thought it was just north/southbound. But its been a while since learning it.

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VapidActions t1_j8ppvb0 wrote

"Up" is relative. Looking at the earth, you're shooting outwards from the sphere (or really irregular elipsoid). By the time the bullet reaches its destination, the planet has turned, resulting in an offset.

The Coriolis effect is a "fictitious force", meaning it's not an actual inertial force, but is calculated as a force based on a frame of reference. In this case, the frame of reference doesn't include the earth's rotation - you can't see that happening, and yet even though the bullet went straight up, something caused it to come back down in a different location, a force, a fictitious force, a Coriolis force.

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GodzlIIa t1_j8qh5zj wrote

Yes so up would mean radially outward. And yea I usually just hear it referred to as the Coriolis effect instead of force.

I'm familiar with doing calculations for an object south/north bound but I don't recall with one travelling vertically upward.

So if I think about it since the angular velocity is constant as you travel vertically but the tangential velocity is not, that would mean a bullet fired up would eventually be travelling slower then the air around it with its East/west component of tangential velocity. Which would push it, but then on the way down I can't help but feel it would have the opposite effect and kind of cancel out.

SO in the northern hemisphere if I shoot a bullet up (radially outward) which direction would it land? Perhaps I'm not understanding it.

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alxwx t1_j8p27m6 wrote

Eh?

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Love_Cannon t1_j8p2udq wrote

The terminal velocity of a bullet is far lower than its muzzle velocity. While it is still enough to kill if it hits you in the right spot, it wouldn't shatter your head as the illustration suggests.

A vacuum implies the absence of air resistance, which would allow the bullet's fall speed to reach its muzzle speed and actually explode heads.

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alxwx t1_j8p3umb wrote

Sure but anything going 50-90m/s (rough terminal velocity of a 9mm) is still going to leave a hell of a mess of the tortoise

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GodzlIIa t1_j8p2s54 wrote

Bullets fired straight up reach terminal velocity on their way down due to air resistance, so this would only happen if there wasn't air resistance. i.e in a vacuum.

(not to undermine lots of people being hurt my stray bullets fired into the air, but they aren't fired straight up)

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Sunspider2 t1_j8p3lk4 wrote

So many people misunderstand this. A normal sized bullet falling on your head....from any height....would certainly hurt and might draw a bit of blood, but won't be fatal.

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LordPeanutButter15 t1_j8pp82z wrote

Listen. I saw an episode of 1000 ways to die that said it’s a real way to die and I’ll believe what I want

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DemetriiOSC t1_j8y3sd1 wrote

Between the years 1985 and 1992, doctors at the King/Drew Medical Center in Los Angeles, California, treated some 118 people for random falling-bullet injuries. Thirty-eight of them died.

Yeah, totally not fatal. Guess they must have been allergic.

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Sunspider2 t1_j8zynhh wrote

You must be allergic to physics and common sense...

If they were seriously injured, it was because the bullets were not fired straight up. They might have been on a downward trajectory, but were still carrying velocity from being fired.

If you doubt this, it is very easy to calculate the energy of a...say...125 grain bullet falling at terminal velocity. You will find it is a tiny fraction of a bullet's muzzle energy, and insufficient to cause serious injury, if the bullet is propelled purely by gravity. That is the point of this discussion, which you missed.

Or, you can continue to make pouty/petulant little arguments with little or no bearing to the topic being discussed. I'm sure that's easier.

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DemetriiOSC t1_j90qfbg wrote

A bullets’ terminal velocity required to penetrate the skin is between 45.1 and 60.0 m/s (148 and 197 ft/s) and bullets traveling at <60.0 m/s (200 ft/s) can penetrate the skull.

In the launch angle region of 80º…90º the bullet basically lands the base first. The terminal velocity might vary between values 40…85 m/s. The result depends on possible Magnus-moment caused bullet instability or the bullet/flow resonance. The buffeting-like phenomenon described is new to the authors of the current paper at this particular context. However, the flow time-dependent phenomena detected were found out to have negligible effect on flight without matching of the natural frequencies (flow/bullet).

Experimental result found for an upwards fired 7.62 mm bullet terminal velocity is about 90 m/s, which is near to the base first landing case simulated result. The typical terminal velocities given in literature for spent bullets are from 300 fps to 600 fps (90...180 m/s).

In many simulated cases through the launch angle region the bullet possessed the estimated minimum lethal energy 40 J at the end of trajectory. The skull penetrating speed 60 m/s was mostly clearly exceeded. A preliminary value for shooter-centered danger zone diameter obtained was found out to be approximately 8 km.

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Sunspider2 t1_j91ozh2 wrote

A bullet fired straight up on Earth, assuming there’s no wind, might still be able to reach a maximum height of around three kilometers (about 10,000 feet), and will then fall back down to Earth. However, just like a human skydiver only accelerates for a few seconds before reaching terminal velocity, the air resistance acting on the bullet will prevent it from reaching speeds even close to muzzle velocity ever again.

Instead, a falling bullet comes back down with a speed of only around 150 miles-per-hour (241 kilometers per hour), which is just 10% of the speed it was fired with. Because of how energy works (proportional to your speed squared), a bullet that falls from high in the air only possesses 1% of the energy of a bullet newly fired from a gun: the equivalent of a brick dropped from a height of just 50 cm (about 20 inches) off the ground.

In terms of speed and energy, this simple treatment does, in fact, correctly give us the properties of a bullet fired up into the air when it hits the ground. But in terms of location, bullets that are fired even straight up can actually come back down up to two miles (about three kilometers) away from where they were fired.

A 150 mile-per-hour bullet won’t be lethal in most instances, but there are two factors that can change the equation dramatically.

Bullets that are fired at an angle, rather than straight up, may never stop and begin tumbling; instead, they can maintain much greater speeds: many hundreds of miles-per-hour.

If a bullet has enough speed to break the skin, it can potentially be lethal; this occurs at different speeds for different bullets and different individual people.

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DemetriiOSC t1_j91vqie wrote

So guess we just cite our sources, piss on em shake hands and call it a day?

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Sunspider2 t1_j9246oe wrote

Lol...no...I admit I was partly wrong. In that while falling bullets are certainly highly unlikely to be fatal, it is possible if all the variables align correctly.

I would contend they are a bit more dangerous than I first thought, but certainly not as dangerous as the initial stats you posted implied....for bullets propelled only by gravity.

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DemetriiOSC t1_j925ni6 wrote

For sure those stats it's pretty much assured they didn't account for angles and just that the location and trajectory showed them that they were from a "celebratory shot".

All I know is if someone is shooting in the air at any angle imma head inside cause I definitely won't rely on those variables not coming together, even in the very unlikely chance that it will hit me as well.

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alxwx t1_j8p3l4z wrote

Terminal velocity for a 9mm is 50-90 m/s … Tortoise still going to smushed

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GodzlIIa t1_j8p4bau wrote

I mean that's pretty slow. Might draw blood for a person. But I suppose for a tortoise might be a bit worse.

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