[sid93]

Originally Posted by redcruiser

I guess the car was doing very high speeds and hence lost traction at the curve.
Also not sure if all the car inmates were belted.
Saw 2 posts one from NPV and yours where cars have lost control on mild curves.
This situation mostly depends on the driver and driving dynamics of the car.

I don't think even the seat belts could have saved them. The roof is almost crushed and yea its due to taking the curve at high speed without knowing the limits of a LUV. I don't know whether it had abs and airbags, but no airbags were deployed. People usually do 100+ on this road and even the speed limit is 100kmph.

[arjithin]

Originally Posted by Thad E Ginathom

Can't argue with the unimpressive NCAP rating, but frankly, the best of cars tend not to do well versus trees.

Simple physics - Collision with a hard/non movable item produces the maximum deceleration (because the vehicle is brought to a full stop almost instantaneously) and hence maximum force on the car and its occupants

Originally Posted by sid93

I don't think even the seat belts could have saved them. The roof is almost crushed and yea its due to taking the curve at high speed without knowing the limits of a LUV. I don't know whether it had abs and airbags, but no airbags were deployed.

The ertiga looks like a it had ABS for sure. The black rims indicate that its V variant (or Z variant produced in 2012) and the presence of Intercooler shows its a diesel. I think this one is a VDi variant.

[Thad E Ginathom]

Originally Posted by arjithin

Simple physics - Collision with a hard/non movable item produces the maximum deceleration (because the vehicle is brought to a full stop almost instantaneously) and hence maximum force on the car and its occupants ... ... ...

It is more than that. It is the area of contact thing. You can push in a drawing pin with your thumb, but try applying that pressure to the sharp end! Your car will do better versus a concrete wall than it will versus a tree.

Also, the tree is very strong, but has just enough give that is unlikely to be knocked down by the car, unless it is old and sick. It is not brittle, but springy. Hey, maybe trees evolved to beat cars in collisions!

(Actually, I think that the truth is that the evolved to get strength and toughness swaying in the wind)

[paragsachania]

Originally Posted by sid93

Its Ertiga BTW and it was fully loaded(7 people on board).

....according to the witness, it went out of control on the curve and rolled many times before coming to stop.

Whatever may have resulted in this gory accident but if the above 2 aspects are factored, The Ertiga with 7 on board, Good Speeds and curves is always a bad combination. There is so much mass traveling inside the car along with it and with such load, you try to negotiate curves at high speeds on indulge in any emergency maneuver is certainly not going to be a cake walk in any manner at all.

Like most of them have mentioned, dynamics change significantly with passenger load: Steering feels heavier, Brakes only feel good but not excellent, there is a lot of body roll with such load when taking turns at high speeds.

We all know how each car changes its behavior with loads inside - There is no real exception to this of defense or pride anyway.

Having driven the Ertiga fully loaded with 7 passengers on ghats that were not only fast and had some faster curves and as well when negotiating a dozen hair pin ascends and descends, It is the experience and judgement that plays an important role on the safety aspects in such conditions. While you think it can maintain some very good speeds like others, you are missing out on the behavioral aspects with 500 Kilos inside.

My driving style changes with 7 on board - Cruising speeds are 10 KMS lesser than usual (Usual =2 rows in use). I am more than just careful in taking on curves or swift lane changes although the latter has no significant change with only driver or full load, it is the stopping power that matters a lot.

With all this, if the vehicle starts toppling at higher speeds, I can only imagine the effects of having 7 on board. It just wont come to rest till a few more topples!

With so many accidents that has resulted in deaths over the past few pages on this thread, I have no hesitation to say that driving is one of the most dangerous activities that we do and each day I learn and continue to learn too.

There are millions of causes for accidents but the primary one being driving itself - Please drive safe!

[keroo1099]

Originally Posted by Thad E Ginathom

It is more than that. It is the area of contact thing. You can push in a drawing pin with your thumb, but try applying that pressure to the sharp end! Your car will do better versus a concrete wall than it will versus a tree.

Also, the tree is very strong, but has just enough give that is unlikely to be knocked down by the car, unless it is old and sick. It is not brittle, but springy. Hey, maybe trees evolved to beat cars in collisions!

(Actually, I think that the truth is that the evolved to get strength and toughness swaying in the wind)

I am skeptical if the car would do better against the concrete wall, as the tree although a 'point' load would give (as you have pointed out) more than the concrete wall and allow the car to dissipate more of the energy
.

I thought this was an interesting test done by Mythbusters:
http://scienceblogs.com/gregladen/20...on-collisions/

1) A car is driven at 50 mph against a solid wall. It gets mushed.

2) A second car is driven at 100 mph against the wall. It gets much more mushed.

3) Two cars are then driven at each other at 50 mph, head-on. They are both mushed the same as the red car shown above. Neither car seems to experience a “100 mph” collision.

Here are the two cars, the red one was driven at 50 mph, the yellow one at 100 mph:

[Thad E Ginathom]

Originally Posted by keroo1099

I am skeptical if the car would do better against the concrete wall, as the tree although a 'point' load would give (as you have pointed out) more than the concrete wall and allow the car to dissipate more of the energy

It gives enough to protect itself, not your car. Almost all reports of collisions with trees that I have read have had nasty consequences, including fatalities. Lamp posts are not good either. The tubular ones may bend and fall, but concrete ones, although they may be damaged, will do worse to the vehicle.

This really is simple physics. In fact, it is simple arithmetic: Pressure = Force / Area.

[keroo1099]

Originally Posted by Thad E Ginathom

This really is simple physics. In fact, it is simple arithmetic: Pressure = Force / Area.

May be going off-topic here but this is what I got when I did a google search.

"The physics of a collision between two bodies is governed by Newton's Second Law of Motion F = ma/gc

where

F = force in pounds or lbf,
m = mass in pound mass or lbm,
a = acceleration in feet per second squared or ft/s2
gc = a proportionality constant of 32.2(lbm•ft/lbf•s2)"

http://www.experts.com/Articles/The-...-Associates-PA

Admit it's not your formula, but Area doesn't factor into the equation at all. Irrespective of the correct interpretation it isn't good, concrete, steel, or tree.

Cheers.

[anupmathur]

Originally Posted by Thad E Ginathom

...
This really is simple physics. In fact, it is simple arithmetic: Pressure = Force / Area.

Originally Posted by keroo1099

...
Admit it's not your formula, but Area doesn't factor into the equation at all. Irrespective of the correct interpretation it isn't good, concrete, steel, or tree.
Cheers.

Ha ha, I think the problem here is of static versus dynamic conditions. Both formulae do apply but in different proportion in each unique situation. Real life mishaps/situations are usually far more complex than theoretical considerations would suggest, and, often, involve other sciences as well, like chemistry, mathematics and the vulnerabilities of human physiology!

[smekad]

Admit it's not your formula, but Area doesn't factor into the equation at all. Irrespective of the correct interpretation it isn't good, concrete, steel, or tree.

Cheers.

It is not the force that causes the metal to shear or deform, it is the pressure. Force applied over a smaller area is going to cause more damage. As they say it is elementary

[Thad E Ginathom]

Originally Posted by smekad

It is not the force that causes the metal to shear or deform, it is the pressure. Force applied over a smaller area is going to cause more damage. As they say it is elementary

That's exactly what I am saying. We do not cut butter with a stick, we use a knife --- and a tree will "cut" it's way into a car in the way that a wall cannot. I suspect that there are many other physical factors involved in such accidents: having "cut" its way through the frontal protection of a vehicle, it can apply pressure to the engine and other components, in ways that walls or other cars will not. To what extent do crumple zones protect against collision with a hard slim object? And then there is the problem of a sliding or spinning car hitting one side-on.

Others can take the maths/physics beyond my basic ability and factor in speed. acceleration, etc, but in the end, a tree or a solid post is still going to come out as one of the nastiest things to drive into.

I think we have a few examples in this thread.

[keroo1099]

Originally Posted by Thad E Ginathom

That's exactly what I am saying. We do not cut butter with a stick, we use a knife

Thinking about it you and smekad are probably right. What you say makes perfect sense, but the strange thing is that you can't find even one comparison on the net about which is worse, hitting a wall or a pole/tree??

Cheers.

[Thad E Ginathom]

Originally Posted by keroo1099

... the strange thing is that you can't find even one comparison on the net about which is worse, hitting a wall or a pole/tree??

Perhaps we have just made up for that here

Was thinking of googling for more information on accidents involving trees, poles, etc. Haven't got around to it yet.

[vnidta]

Originally Posted by keroo1099

F = ma/gc

Hmmm.., let's just ignore the real physics and mathematics of these stuff and think like our Bangalore (or any other city) cabbies... For them, this formula seems to expand in this way...

F = Faster speeds to reach destination

ma = My Acceleration
gc = Ground Clearance


So, this seems to be the formula that our cabbies strictly follow. The higher the ground clearance, the more one has to accelerate in order to achieve better speeds to reach destination

No wonder the Yellow Board Innovas, Xylos, Wingers and Sumos today are reckless

[IshaanIan]

Originally Posted by redcruiser

Saw 2 posts one from NPV and yours where cars have lost control on mild curves.
This situation mostly depends on the driver and driving dynamics of the car.

Originally Posted by Thad E Ginathom

As I always say: cars don't loose control: drivers do!

But the worst of cars, even with the worst of drivers, should be able to take anything the Chennai Outer Ring Road can throw at it

Apart from the handful of enthusiasts that exist, I see most people learning how to drive in driving schools; being taught to depress the clutch while braking all the time (sadly I see a lot of "enthusiasts" also that love their cars but when it comes to driving, all they've got are balls of steel for straight line speed, most don't know how to navigate a curve properly). This ensures that they never understand the effects of remaining in gear or shifting down while shedding speed or how its effects on the car's levels of front-end traction and weight balance, help it go around a bend. I keep seeing posts about cars losing control on a highway and shake my head lives being lost simply because no one had the time or the inclination to teach them the skills needed to drive a car properly. Vernas, Ertigas, BMWs and what not. When I can do such things in my WagonR in a very controlled manner, it really disappoints me to hear of people losing control in such cars.

[Thad E Ginathom]

Originally Posted by IshaanIan

I keep seeing posts about cars losing control on a highway and shake my head

It's the common way of putting it. It is what people read in the media. As such, it means nothing, unless, like me, you believe that words have a deeper influence, and every time someone reads this it reinforces the idea that the car is responsible, not the driver.

And so this thread will never be short of content.