Azhais posted:

Azhais posted:

Nordick posted:

PYF Bad rear end Pictures: Cast All Medals into Spearheads of Revolution

ultrafilter posted:

https://www.youtube.com/watch?v=1y2Asd5_ito

chitoryu12 posted:

https://i.imgur.com/Ezyqew1.mp4

Panfilo posted:

Wuh? How?

Panfilo posted:

Wuh? How?

Azhais posted:

Azhais posted:

DontMockMySmock posted:

To maintain a circular trajectory, an object must have an acceleration towards the center of the circle equal to its speed squared divided by the circle's radius (v²/R). If there's too much acceleration, then the car will fall towards the center of the circle (bad news). Let's consider the most dangerous point, the very top of the loop, where gravity points straight towards the center of the circle. There are two sources of acceleration: gravity and the contact force between the car and the track. The contact force can't pull upwards, though, so at the critical threshold where the car barely makes the loop, it will be zero and gravity will be doing all the work. So we can solve the equation g = v²/R, where g is the acceleration due to gravity on Earth's surface (9.8 m/s² or 32 ft/s²) to find the critical speed v where the car barely is going fast enough to make the loop.

Rearranging that equation, we get v = sqrt(g*R).

Estimating based on the video that the loop is about 3 and a half car lengths in diameter, and using a value I googled of 4.5m for the length of a car, we get v = sqrt(9.8 m/s² * 4.5m * 3.5/2) = 8.8 m/s or 19.7 miles per hour.

This doesn't sound like much, and it isn't! In practice, they probably want to be going a fair bit faster for a healthy safety margin. However, they've also got the problem that as they rise through the loop, they lose speed, or in other words, some of their kinetic energy is converted into gravitational potential energy. Assuming that they don't either lose speed to friction or gain speed from their engine during the loop (a bad assumption but the two effects will at least partially cancel out), we can use conservation of energy to figure out how fast they should be going at the bottom of the loop.

KE_before + PE_before = KE_after + PE_after

1/2 m v[sub[before[/sub]² + m g (0) = 1/2 m v[sub[after[/sub]² + m g h

(We can divide through to cancel the masses; the initial height is zero, the final height will be 3.5 car lengths; the speed after will be our 8.8 m/s.)

1/2 v_before² = 1/2 (8.8 m/s)² + (9.8 m/s²)*(3.5*4.5m)

v_before = sqrt[(8.8 m/s)² + 2*(9.8 m/s²)*(3.5*4.5m)]

which comes out to 19.7 m/s or 44.0 miles per hour.

This is all heavily estimated, of course - this is more of an example than a serious analysis of the video. You could get way more accurate measurements if you opened it up in image-editing software and measured pixels and stuff. I did my best to do a quick-and-dirty measure of their speed in the video and I'd say it looks like they were going about 45-55mph at the bottom, which seems like not a lot of margin for error, so probably the circle was a bit smaller than I was estimating, or maybe they get enough of a boost by gunning the engine through the loop itself. Either way, as you can see from these example numbers, it's surprisingly doable. The hardest part is probably getting their insurance company to sign off on this stunt, as if anything goes wrong, you could have someone in a car falling fifty feet, landing with much more force than a car's roll cage is normally meant to handle. So that's probably one good reason why you don't see this stunt done more often - it's surprisingly easy to do, but dangerous as hell.

DontMockMySmock posted:

To maintain a circular trajectory, an object must have an acceleration towards the center of the circle equal to its speed squared divided by the circle's radius (v²/R). If there's too much acceleration, then the car will fall towards the center of the circle (bad news). Let's consider the most dangerous point, the very top of the loop, where gravity points straight towards the center of the circle. There are two sources of acceleration: gravity and the contact force between the car and the track. The contact force can't pull upwards, though, so at the critical threshold where the car barely makes the loop, it will be zero and gravity will be doing all the work. So we can solve the equation g = v²/R, where g is the acceleration due to gravity on Earth's surface (9.8 m/s² or 32 ft/s²) to find the critical speed v where the car barely is going fast enough to make the loop.

Rearranging that equation, we get v = sqrt(g*R).

Estimating based on the video that the loop is about 3 and a half car lengths in diameter, and using a value I googled of 4.5m for the length of a car, we get v = sqrt(9.8 m/s² * 4.5m * 3.5/2) = 8.8 m/s or 19.7 miles per hour.

This doesn't sound like much, and it isn't! In practice, they probably want to be going a fair bit faster for a healthy safety margin. However, they've also got the problem that as they rise through the loop, they lose speed, or in other words, some of their kinetic energy is converted into gravitational potential energy. Assuming that they don't either lose speed to friction or gain speed from their engine during the loop (a bad assumption but the two effects will at least partially cancel out), we can use conservation of energy to figure out how fast they should be going at the bottom of the loop.

KE_before + PE_before = KE_after + PE_after

1/2 m v[sub[before[/sub]² + m g (0) = 1/2 m v[sub[after[/sub]² + m g h

(We can divide through to cancel the masses; the initial height is zero, the final height will be 3.5 car lengths; the speed after will be our 8.8 m/s.)

1/2 v_before² = 1/2 (8.8 m/s)² + (9.8 m/s²)*(3.5*4.5m)

v_before = sqrt[(8.8 m/s)² + 2*(9.8 m/s²)*(3.5*4.5m)]

which comes out to 19.7 m/s or 44.0 miles per hour.

This is all heavily estimated, of course - this is more of an example than a serious analysis of the video. You could get way more accurate measurements if you opened it up in image-editing software and measured pixels and stuff. I did my best to do a quick-and-dirty measure of their speed in the video and I'd say it looks like they were going about 45-55mph at the bottom, which seems like not a lot of margin for error, so probably the circle was a bit smaller than I was estimating, or maybe they get enough of a boost by gunning the engine through the loop itself. Either way, as you can see from these example numbers, it's surprisingly doable. The hardest part is probably getting their insurance company to sign off on this stunt, as if anything goes wrong, you could have someone in a car falling fifty feet, landing with much more force than a car's roll cage is normally meant to handle. So that's probably one good reason why you don't see this stunt done more often - it's surprisingly easy to do, but dangerous as hell.

Panfilo posted:

Nordick posted:

PYF Bad rear end Pictures: Cast All Medals into Spearheads of Revolution

DontMockMySmock posted:

which comes out to 19.7 m/s or 44.0 miles per hour.

krinklechip posted:

Nordick posted:

PYF Bad rear end Pictures: Cast All Medals into Spearheads of Revolution

Snowglobe of Doom posted:

Well here's a sound I never ever want to hear in real life: an angry King Cobra growling

https://i.imgur.com/jsDLEZb.mp4

Maximum Sexy Pigeon posted:

ACAB, but this is fkn badass

https://twitter.com/LAPDHQ/status/1480363436311670784

Lady Disdain posted:

Is there seriously no way to communicate with trains that there's something on the track up ahead ? Like the emergency stop button on an escalator.

Biplane posted:

Would have been cool and badass if the cops died. Maybe the pilot too, I don't know anything about him but he's old, white, and wealthy enough to own a plane so probably he is at least as racist and stupid as the cops.

CyberPingu posted:

What the gently caress is wrong with you...

Lady Disdain posted:

Is there seriously no way to communicate with trains that there's something on the track up ahead ? Like the emergency stop button on an escalator.