## South African Skeptics

December 06, 2019, 22:07:38 PM
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# 234 km/h

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Mefiante
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In solidarity with rwenzori: Κοπρος φανεται

 « Reply #15 on: December 06, 2010, 15:50:33 PM »

If you include "reaction time/distance" in the formula, then yes.
You can derive the formula from first principles with a basic knowledge of high school kinematics.  The formula is (and you can check its validity for yourself by dimensional analysis):

sS = v0tR + ½∙mv02/FB

where

sS ― total stopping distance (metres);
v0 ― velocity of the vehicle before braking commences (metres per second);
tR ― driver’s reaction time (seconds);
m ― vehicle’s mass (kg); and
FB ― constant braking force (Newtons).

For example, a 1,500 kg vehicle travelling at 34 m/s (= 122 km/h) whose brakes and tyres are capable of exerting 10 kN (= 10,000 N) of braking force will have a total stopping distance of about 104 metres if the driver’s reaction time is half a second.  At half that speed with everything else being equal, the stopping distance is a little over 30 metres.  At twice the speed, the stopping distance is 381 metres.

Clearly, the dominant term on the right-hand side is the second one, which is quadratic in v0, and if you neglect the reaction time, the first term on the right-hand side falls away completely, making the formula a pure quadratic in v0.

'Luthon64
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Lilli
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 « Reply #16 on: December 07, 2010, 08:26:54 AM »

Regardless of the fancy mathematics - fact remains: it is not speed that kills. It's stopping very suddenly that's the bitch...
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StevoMuso
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 « Reply #17 on: December 08, 2010, 10:17:19 AM »

Regardless of the fancy mathematics - fact remains: it is not speed that kills. It's stopping very suddenly that's the bitch...
LOL. Good one Lilli. Maybe it's how fast you stop that kills, heheh.
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Tweefo
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 « Reply #18 on: December 08, 2010, 17:50:18 PM »

In my skydiving days I've seen (twice) what the last cm can do. Not a pretty sight.
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Watookal
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 « Reply #19 on: December 08, 2010, 21:05:30 PM »

I bet that leaves quite an impression.
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Tweefo
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 « Reply #20 on: December 09, 2010, 12:45:28 PM »

I bet that leaves quite an impression.
Terminal velocity for a human is around 200 - 300 km/h depending on the body position. You go in at that speed with no crumple zones... The 1st one I saw was suppose to do a 5 second delay and then open his parachute. He never did. The second one had something like a hundred jumps, so relatively experienced, pulled his pilot chute just before "bouncing" but that did not even slowed him down. Now they jump with a thing that pull your reserve parachute if you go to fast past a certain height. These things were available in my days but very expensive, so I never had one. I've done about 500 jumps (got lazy in logging towards the end) about 20 military jumps (I was a parrabat for my 2 year diensplig and if you meet me you will not believe it) and one base jump. I was number 13 to jump off Blauwkrans bridge.
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Rigil Kent
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 « Reply #21 on: December 09, 2010, 20:51:54 PM »

Terminal velocity for a human is around 200 - 300 km/h
Lilli already established that terminal velocity is a mere 0km/h.

I think its a good time to quit now: you know, bell curves and all that.

But more importantly ... who would have thought ... Tweefo an epinephrine aficionado .

Mintaka
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Tweefo
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 « Reply #22 on: December 10, 2010, 10:13:40 AM »

Terminal velocity for a human is around 200 - 300 km/h
Lilli already established that terminal velocity is a mere 0km/h.

I think its a good time to quit now: you know, bell curves and all that.

But more importantly ... who would have thought ... Tweefo an epinephrine aficionado .

Mintaka

I've had my moments, nothing like a bit of air up the nose.
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Lilli
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 « Reply #23 on: December 13, 2010, 13:15:38 PM »

Returning to topic somewhat... I would not ever drive on the German autobahn if I could at all help it, because I don't like going so fast - it makes me nervous. Other people's cars might be able to reach such speeds, and it might be safe, but I drive a piece of affordable crap with an 1100 engine. Additionally, other people might be able to drive so well that reaching 234km/h is not dangerous for them, but I can not, I feel uncomfortable going much faster than 100. (must be because I'm a female driver...) Point is, there has to be rules of the road, and there are several reasons why we have the rules we have, and this guy broke the rules in a big way. He should pay the consequences in my opinion.
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SKEPRat
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 « Reply #24 on: December 13, 2010, 17:57:27 PM »

Lilli, Theres no problem driving slower on an autobahn. Just maintain the minimum speed in the slow lane and you're OK. The rules are exactly the same as for highways in SA except that SA drivers either don't know or refuse to obey the rules.
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Lilli
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 « Reply #25 on: December 14, 2010, 08:09:14 AM »

Lilli, Theres no problem driving slower on an autobahn. Just maintain the minimum speed in the slow lane and you're OK. The rules are exactly the same as for highways in SA except that SA drivers either don't know or refuse to obey the rules.
OK fair enough - I don't know the rules of the autobahn. I just freak out completely when I go into a faster lane on the highway (I avoid the fast lane at all costs) to overtake a car/driver even slower than me, and then suddenly there's a guy weaving across all available lanes, flashing his lights, overtaking people on the left etc etc because its MUCH more important for that guy to get to where he is going. I think that this particular guy was not driving 234 km/h because he and his car are capable of doing such speeds and he wasn't being any kind of threat/risk on the road. I think he was a self-important asshole who would've given me a heart attack if I'd been on that road at that time, and I would've used very creative words to express my emotions if that were the case.
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Tweefo
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 « Reply #26 on: December 14, 2010, 09:43:13 AM »

Quote
I think that this particular guy was not driving 234 km/h because he and his car are capable of doing such speeds and he wasn't being any kind of threat/risk on the road. I think he was a self-important asshole who would've given me a heart attack if I'd been on that road at that time, and I would've used very creative words to express my emotions if that were the case.

Thank you Lilli
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Mefiante
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In solidarity with rwenzori: Κοπρος φανεται

 « Reply #27 on: December 14, 2010, 21:42:19 PM »

… then suddenly there's a guy weaving across all available lanes, flashing his lights, overtaking people on the left etc etc because its MUCH more important for that guy to get to where he is going.
That type of driver behaviour would in any case not be tolerated by the German highway patrol (or that of any other European country), irrespective of either the speed limit (if there is one) or the type of road.  It’s all about effective policing and enforcing appropriate driver discipline.

'Luthon64
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