Physics Question

[Arpeggio]

Would you rather be hit by a train at 20mph or a pillow at 150mph?

[oracle]

11 hours ago, Arpeggio said:

Would you rather be hit by a train at 20mph or a pillow at 150mph?

pillow at 150mph for sure.

1) Force = mass * velocity^2.(taking approximations of 1mph=1.6kmh and 1kg= 10N)

  for the train......lets say 100 tonnes,  so 100000*32*32 =10,240,000,000,000N

for the pillow...lets say 1kg  so 1*240*240=57,600N

2) pillows have much greater elastic potential than steel,meaning some of that force springs away from the direction of travel on contact!...the only thing squishy in the other situation is your innards.

[oracle]

might be a slightly better physics question for you here:

Would you rather have an ashiatsu massage(back walking type)  from:

a) Lizzo in a pair of DM's

b)Amanda Holden in stillettos

[longgone]

no physics involved 

the pillow will stop the train won`t at 5mph the train will still kill you.  

[Arpeggio]

On 23/05/2020 at 09:31, oracle said:

might be a slightly better physics question for you here:

Would you rather have an ashiatsu massage(back walking type)  from:

a) Lizzo in a pair of DM's

b)Amanda Holden in stillettos

I need more information in order to answer that. Would the gimp suit be made of leather and / or have a good coverage on my back?

[Arpeggio]

On 23/05/2020 at 12:43, longgone said:

no physics involved 

the pillow will stop the train won`t at 5mph the train will still kill you.  

I disagree with that.

[longgone]

10 hours ago, Arpeggio said:

I disagree with that.

fire a pillow into the sky 

[Megadebt]

On 23/05/2020 at 09:12, oracle said:

pillow at 150mph for sure.

1) Force = mass * velocity^2.(taking approximations of 1mph=1.6kmh and 1kg= 10N)

  for the train......lets say 100 tonnes,  so 100000*32*32 =10,240,000,000,000N

for the pillow...lets say 1kg  so 1*240*240=57,600N

2) pillows have much greater elastic potential than steel,meaning some of that force springs away from the direction of travel on contact!...the only thing squishy in the other situation is your innards.

Newtons 2nd   F=MA   gives the inertia, in Newtons required for an acceleration A (or deceleration here)

1/2 mv2 the kinetic energy, in Joules for change in momentum.

I'd say the derivative of acceleration J the impulse  in kgms,  Integrating between impact on off times t1   and t2  gives force  applied at impact. 

 

Impulse J produced from time t₁ to t₂ is defined to be^[2]

where F is the resultant force applied from t₁ to t₂.

From Newton's second law, force is related to momentum p by

So assuming that the amount 1000 ton train that would be slowed slightly by any impact could be precisely measured, that impulse is the total force applied at impact.

Generally there is a big step in pedestrian road traffic deaths in being hit between 20 and 30 mph. So thinking a train collision, if knocked out the way instead of being splattered (amount work done in the impulse) could likely be survivable.

 

 The pillow at 150 mph has HUGE  kinetic energy, that V squared function. 

The pressure  (force divided by area) applied by the pillow on small contact area would be much greater to causing more trauma.

So I'd go with the train.

 

 

  According to the Guiness World Records, the "fastest martial arts punch in the world was 43.3 mph" or 19 mps.

.

[Arpeggio]

2 hours ago, Megadebt said:

Generally there is a big step in pedestrian road traffic deaths in being hit between 20 and 30 mph. So thinking a train collision, if knocked out the way instead of being splattered (amount work done in the impulse) could likely be survivable.

 The pillow at 150 mph has HUGE  kinetic energy, that V squared function. 

The pressure  (force divided by area) applied by the pillow on small contact area would be much greater to causing more trauma.

So I'd go with the train.

I was wandering the same. There was nothing in my question that suggested the person was stuck to the ground. Also the weight of the person; someone heavier will have more opposing force.

 

2 hours ago, Megadebt said:

According to the Guiness World Records, the "fastest martial arts punch in the world was 43.3 mph" or 19 mps.

Interesting. It's more about the momentum behind it then. Also if you clench your fist only on contact (loose fist just before). It takes some practise getting the timing right, your front fist detects contact with target before clench. It's a bit like a smashing the end of a piece of wood on concrete, it will eventually split the grain and break. If you put a sandbag over the end, the sand will compress on contact and give protection to the wood, while transferring the force.

Do you know about / interested in cavitation?

https://www.sciencenewsforstudents.org/article/shrimp-packs-punch

[Megadebt]

Actually the total kinetic energy absorbed over time divided by the area, and a co-efficient of elasticity of both objects ...and other unknown factors.  I think.

The angry squid in the link works by hitting very fast, big Kinetic energy and rock hard nippers

Kinetic energy = 1/2 mv squared    squid has small m   but massive v squared.  

A bulletproof vest spreads the impact and absorbs some of the energy - same lethal kinetic energy, just spread to a further area and absorbed over a longer impulse time. Getting shot in bulletproof vest won't kill you but could still result in broken ribs.

 Cavitation is fluid dynamics,  seems so complex and almost choatic, normally found through lab testing rather numerical analysis. Has many real world applications: lots of the natural world uses sciences we apply in engineering

 

[longgone]

standing between the tracks how fast does a train have to go to kill you ?

[Sledgehead]

6 hours ago, Megadebt said:

Newtons 2nd   F=MA   gives the inertia, in Newtons required for an acceleration A (or deceleration here)

1/2 mv2 the kinetic energy, in Joules for change in momentum.

I'd say the derivative of acceleration J the impulse  in kgms,  Integrating between impact on off times t1   and t2  gives force  applied at impact. 

 

Impulse J produced from time t₁ to t₂ is defined to be^[2]

where F is the resultant force applied from t₁ to t₂.

From Newton's second law, force is related to momentum p by

So assuming that the amount 1000 ton train that would be slowed slightly by any impact could be precisely measured, that impulse is the total force applied at impact.

Generally there is a big step in pedestrian road traffic deaths in being hit between 20 and 30 mph. So thinking a train collision, if knocked out the way instead of being splattered (amount work done in the impulse) could likely be survivable.

 

 The pillow at 150 mph has HUGE  kinetic energy, that V squared function. 

The pressure  (force divided by area) applied by the pillow on small contact area would be much greater to causing more trauma.

So I'd go with the train.

 

 

  According to the Guiness World Records, the "fastest martial arts punch in the world was 43.3 mph" or 19 mps.

.

At least you are thinking correctly, which oracle was, sadly, not.

I am reminded of the demonstration of firing a cigar, loaded into a shotgun,  through a solid wooden door ..

Usain Bolt tops 27mph. Does that mean if he runs into a brick wall (inertia  larger than a train - unless he knocks it down), he will definitely injur himself?

The OPs q is an odd question in that it doesn't make clear whether one is allowed to anticipate the impact. Most people could absorb much of the train impact in their arms. Not much chance of that with the pillow.

 

[Megadebt]

23 minutes ago, Sledgehead said:

Usain Bolt tops 27mph. Does that mean if he runs into a brick wall (inertia  larger than a train - unless he knocks it down), he will definitely injur himself?

The OPs q is an odd question in that it doesn't make clear whether one is allowed to anticipate the impact. Most people could absorb much of the train impact in their arms. Not much chance of that with the pillow.

 

Yes. Resultant injuries a function of his his co-efficient of elasticity? 

Nature tells us to brace with our arms to protect the head in an accident or crash -did it myself, broke both arms but nothing wrong with my head ?

Quite amazed that the nanny state even allows Pillows anymore.

 

 

[Arpeggio]

3 hours ago, Megadebt said:

Actually the total kinetic energy absorbed over time divided by the area, and a co-efficient of elasticity of both objects ...and other unknown factors.  I think.

The angry squid in the link works by hitting very fast, big Kinetic energy and rock hard nippers

Kinetic energy = 1/2 mv squared    squid has small m   but massive v squared.  

A bulletproof vest spreads the impact and absorbs some of the energy - same lethal kinetic energy, just spread to a further area and absorbed over a longer impulse time. Getting shot in bulletproof vest won't kill you but could still result in broken ribs.

Yes lots of variables that would have to be taken into account. Apparently the pistol shrimp uses cavitation to dramatically increase its punch power. Similar to the bubbles that form around an underwater propeller despite being completely submerged underwater.

I suppose there are lot's of examples of surface area and force, like it must be difficult for a ballet dancer being on tip toes. Another variable would be the density of one of the impact objects, for instance water, which is why belly flopping into the water is painful despite spreading ones surface area! while diving with minimal surface area is less painful.

 

3 hours ago, Megadebt said:

Cavitation is fluid dynamics,  seems so complex and almost choatic, normally found through lab testing rather numerical analysis. Has many real world applications: lots of the natural world uses sciences we apply in engineering

It is intriguing. Nature can even create things from apparently nothing.

"William Prout (1785–1850): Studied incubating chickens and found that hatched chicks had more lime (calcium) in their bodies than originally present in the egg, which was not contributed from the shell."

Regarding natural sciences used in engineering it looks like the Casimir effect used by Geckos is used by NASA also. https://www.greenmedinfo.com/blog/new-biophysics-deep-dive-quantum-rabbit-hole-esoteric-physiology-01

Also from that link:

"Mark LeClair, a scientist specializing in harnessing water cavitation for nanotechnological applications, came upon a revolutionary discovery when he performed a series of grant-funded experiments using a laser to induce cavitation bubbles. An unexpected result of the experiment was the production of excessive energy (evidence of zero-point energy harnessing), with 840 watts powering the pump and 2,900 watts produced."

Energy can neither be created or destroyed? Maybe that is E = MC2 in action and it's actually mass transferring into energy?

The weird fractal like picture at the top of that website is a kind of broccoli I am growing some at the moment.

[Arpeggio]

41 minutes ago, Sledgehead said:

Usain Bolt tops 27mph. Does that mean if he runs into a brick wall (inertia  larger than a train - unless he knocks it down), he will definitely injur himself?

Surely yes he would I'd think, unless his hands can contact the wall and his arms act as suspension to spread the deceleration over greater time.

[Arpeggio]

1 hour ago, longgone said:

standing between the tracks how fast does a train have to go to kill you ?

The pillow traveling at 150mph knocks you out of the way just before impact. Although in the process, unfortunately the pillow glances your chin and causes you to bite your lip.

[Sledgehead]

1 hour ago, Arpeggio said:

Surely yes he would I'd think, unless his hands can contact the wall and his arms act as suspension to spread the deceleration over greater time.

He's got quite big arms, like all sprinters. But something tells me I'm barking up the wrong tree when I imagine they work on their arms just in case a wall should happen along in front of them from time to time ... ?

[longgone]

29 minutes ago, Arpeggio said:

The pillow traveling at 150mph knocks you out of the way just before impact. Although in the process, unfortunately the pillow glances your chin and causes you to bite your lip.

is the pillow polyester fillings, down, or memory foam ?

[Arpeggio]

2 minutes ago, longgone said:

is the pillow polyester fillings, down, or memory foam ?

It is indeed memory foam. You know this when looking to see your face imprinted on it.

[Sledgehead]

1 hour ago, longgone said:

is the pillow polyester fillings, down, or memory foam ?

rocks: he's dead 'ard, our Arpeggio

[Arpeggio]

13 minutes ago, Sledgehead said:

rocks: he's dead 'ard, our Arpeggio

Yeah, and snakes. Dead 'ard....and Viagra to stop me rolling out of bed at night.

[longgone]

39 minutes ago, Arpeggio said:

It is indeed memory foam. You know this when looking to see your face imprinted on it.

well if its an old piss stained pillow it would probably slide right off your face like teflon. 

[Mikhail Liebenstein]

On 28/05/2020 at 19:49, Megadebt said:

Yes. Resultant injuries a function of his his co-efficient of elasticity? 

Nature tells us to brace with our arms to protect the head in an accident or crash -did it myself, broke both arms but nothing wrong with my head ?

Quite amazed that the nanny state even allows Pillows anymore.

 

 

 

Yes, the elasticity is important. Somewhat reminds me of this famous story:

https://www.snopes.com/fact-check/catapoultry/

 

 

 

[Si1]

On 28/05/2020 at 18:15, longgone said:

standing between the tracks how fast does a train have to go to kill you ?

https://www.bbc.co.uk/news/business-46040056