[electric_eel]

People often underestimate how bad speed is when it comes to injury. Here is a quick "conversion" of speed to equivalent height from which you need to jump to get the same effect (or may be defect is the right word here).

If one is thrown out of a car (because of lack of belting up or worse sticking out of the sun roof) at a speed v then the kinetic energy is 1/2 m v^2. This is equivalent to jumping out from a building of height h = 1/2 m v^2 / mg. = 1/2 (v^2) g. For ease of calculation we can take g = 10 m/s^2 then we get for v = 10 m/s = (36 Km /h) the height is 5 m (almost a 2 storey building 1 storey approx 3 m ). But what is worse is if one doubles the speed = 20 m/s (72 Km /h) it is equavlent to 20 * 20 /20 = 20 m which is approximately 6 floors (3 floors = 10 m).

i.e at a nominal highway speed of about 70 km/h a crash is equivalent to jumping out of
a 6-storey building. I shudder to think of people casually saying that they drive at 120+ (a relatives biggest gripe with cruise control was that it does not allow one to go above 120).

[GTO]

Thanks for sharing! Perhaps, the best illustration of that is in this video:

https://www.youtube.com/watch?v=libNxDwHJoo

[AutoNoob]

Adding real crash test videos: 40mph (64 kmph) vs. 56mph (90 kmph) for reference.

https://m.youtube.com/watch?v=bWhdkvWkqao

[NomadSK]

Mathematically, your point is correct with respect to the non-living things and with regards to the energy dissipation. However, you have totally missed an important aspect, the capabilities of human body to react to various G's. In this case, you are comparing forward G to downward G (or zero G here).

A human body is well capable to handle/absorb forward G's as compared to the downward G or heck the most dangerous is the negative G. As you may expect, our body's physiology will both be affected by and respond to this variability in the G forces. So basically, the comparison you have made is similar to comparing "apple and oranges".

That's why a head-on collision is much safer than T-boning at the same speed or falling off a bridge.

[chaitanyakrish]

The BBC made a documentary that's highly recommended for anyone curious about how safety systems are added to cars. You can watch it here:

link

.
Ralph Nader deserves recognition for his work in challenging General Motors and pushing for the first US automobile safety law in 1966. His book titled "Unsafe at Any Speed" is widely known.

[electric_eel]

Originally Posted by NomadSK

Mathematically, your point is correct with respect to the non-living things and with regards to the energy dissipation. However, you have totally missed an important aspect, the capabilities of human body to react to various G's. In this case, you are comparing forward G to downward G (or zero G here).

Humans can withstand quite a bit of G force. Fighter pilots can withstand much more (I do not know the numbers) but this is not what we are talking about. It is the speed at which at which you hit the wall. My point is if you are for example thrown out of the car
due to lack of belting or sunroof riding and hit a kerb then at 72 kmph it is like doing a
dive into the kerb from 6 floors. The science says this and the effects will not be any different. Now you may impact with head first, belly first and might be lucky and fall on freshly harvested cotton. But the same luck can work for you when you jump from 6 floors.

A human body is well capable to handle/absorb forward G's as compared to the downward G or heck the most dangerous is the negative G. As you may expect, our body's physiology will both be affected by and respond to this variability in the G forces. So basically, the comparison you have made is similar to comparing "apple and oranges".

This has nothing to do with G. It has got to do with how the energy (which is the same in both cases) taken out (is it a soft or a hard impact). Most people are saved in a head on collision due to a combination off many reasons.

1. both the drivers pressed the brake and reduced the speed at the last moment

2. Body design, safety features like seat belt, air bags etc.


But if you are thrown out then the result will be the same. So my point is

1. Take necessary safety mechanism
2. Control your speed.


Here is another "fun" fact. If you jump out of a plane without parachute then you can get the "thrill" of hitting the ground at 200 Kmph. At normal pressure with belly to the ground it seems the terminal velocity is about 200 kmph. You can go faster of course.

https://www.fai.org/page/isc-speed-skydiving

So before you do the 200 kmph runs just think of it as jumping out of the plane.

[electric_eel]

Originally Posted by chaitanyakrish

The BBC made a documentary that's highly recommended for anyone curious about how safety systems are added to cars. You can watch it here: link.
Ralph Nader deserves recognition for his work in challenging General Motors and pushing for the first US automobile safety law in 1966. His book titled "Unsafe at Any Speed" is widely known.

Great documentary. The thing about coma in side impact also explains a case that I heard of and which I have described

https://www.team-bhp.com/forum/road-...ml#post5606672 (Accidents in India | Pics & Videos)

[chaitanyakrish]

Originally Posted by NomadSK

the capabilities of human body to react to various G's.

Human body can withstand a lot of G force, only when it comes to a safe stop in a certain amount of time, however, it cannot withstand the same G force when it comes to a stop in a short period of time.

We are missing the time factor in the analysis.

Quoting Jeremy Clarkson — 'Speed has never killed anyone. Suddenly becoming stationary, that's what gets you.'

[NomadSK]

Originally Posted by electric_eel

This has nothing to do with G. It has got to do with how the energy (which is the same in both cases) taken out (is it a soft or a hard impact). Most people are saved in a head on collision due to a combination off many reasons.

1. both the drivers pressed the brake and reduced the speed at the last moment

2. Body design, safety features like seat belt, air bags etc.

Thank you. All this what you have mentioned is related to the "G forces" on the human body. Although you may say, driver has braked, car has come to a halt, is wearing seat belt or taken any safety mechanism.

Moreover, your example for fighter pilot is a bit skewed here, as in air, one will be facing through 3-dimensional G-forces. While in case of road cars, they operate in a 2-dimensional plane.

You have done the "physics" behind the accident but have completely neglected the anatomy of human body.

But if you are thrown out then the result will be the same. So my point is

1. Take necessary safety mechanism
2. Control your speed.

There's no doubt about this.

Originally Posted by chaitanyakrish

Human body can withstand a lot of G force, only when it comes to a safe stop in a certain amount of time, however, it cannot withstand the same G force when it comes to a stop in a short period of time.

We are missing the time factor in the analysis.

You guys have missed my point here, All I'm saying the capabilities of "human body anatomy" to deal with G forces in various directions. Be it Forward/Lateral/Upward/downward. Considering the time frame same, speed same, a human body can withstand higher G forces in forward direction as compared to lateral/upward or downward direction.

Nothing more to add here. Thanks for listening

[electric_eel]

Originally Posted by NomadSK

Thank you. All this what you have mentioned is related to the "G forces" on the human body. Although you may say, driver has braked, car has come to a halt, is wearing seat belt or taken any safety mechanism.

Moreover, your example for fighter pilot is a bit skewed here, as in air, one will be facing through 3-dimensional G-forces. While in case of road cars, they operate in a 2-dimensional plane.

I do not think G-force is relevant. What one means by G force is the "fictional" force that one feels when accelarating. For example, when a lift start moving (and thereby accelarating) you suddenly feel that your weight has increased. Similarly when the lift starts moving downwards you feel a sudden loss of weight. These are the G-force in action. As you see G-force has nothing to do with the situation of interest.In fact when you free fall you are actually weightless (just like when you are orbiting in a satellite).

My sole purpose was to give a height equivalent of speed because I have always felt that people take jumping from 6 storey building more seriously than being thrown out at a measly 70 Kmph. Similary, I hear people doing 180-200 Kmph on kerala highway (one of my relatives). Do they really understand the consequence of this (equivalent to jumping out of an airplane) ?Would they still consider themselves as a "safe" driver after these irrefutable facts ?

[rroy92]

Originally Posted by GTO

Thanks for sharing! Perhaps, the best illustration of that is in this video:
https://www.Youtube.com/watch?v=libNxDwHJoo

In case someone is interested this seems to be from BeamNG Drive

[FLYBOYSID]

Originally Posted by NomadSK

You guys have missed my point here, All I'm saying the capabilities of "human body anatomy" to deal with G forces in various directions. Be it Forward/Lateral/Upward/downward. Considering the time frame same, speed same, a human body can withstand higher G forces in forward direction as compared to lateral/upward or downward direction.

Nothing more to add here. Thanks for listening

It does feel that people go great lengths to justify their acts, and at times rightly so. No one cares about the number of Gs you experience as long as they don’t get to you.

You are absolutely right about different G tolerances in vertical, lateral and transverse axis. However, these values are peanuts compared to what you experience in severe crashes. Even fighter pilots and formula one drivers (I am one of the two) don't go anywhere close to that regime.

For general understanding, we are talking of G here as the deceleration/ g(i.e. 9.8 m/s2). But human anatomy is also susceptible to the area where these ‘G’ is applied. Point forces will tear the human body and shatter the bones. (Even the Jimny could not take point loads against the Bolero pick up)Nothing against the Jimny, point is it was an engineered metal piece. Therefore, human anatomy considered, high Gs in crashes will still hurt a lot.
So drive safe, you will never be able to calculate the Gs you will experience in a crash. Too many variables for the human mind to work out in a split second.

[holdoyn]

I like this simple analogy from Neil DeGrasse Tyson regarding speed and seat belts:
IMO, very effectively conveyed.

https://www.youtube.com/watch?v=n5C-XymHJtQ