Posted on 06/30/2010 4:09:44 AM PDT by Teacher317
Glad to hear that it was the rear door and not yours. How did your son take it?
The formula you should use is impulse-momentum: mv1+Fdt = mv2. Your truck's mass is slowed from v1 to v2 (zero). This would yield the average force the Saturn exerted on you over the collision. Note that the greater the time, the less force (and also the less acceleration) you would experience. This is where the engineers' work paid off.
BTW, glad you're alive.
BTW: I asked about Midwest time because Teacher317 has an Indiana logo on their FR About page. I don’t know what I was thinking about 14 hours ago from now being in the AM. I think I must have took 12 hours (+2) to be 24 (+2) hours (in my not yet caffeinated brain).
Wow, what a horrible experience. Glad you made it, prayers for the one that didn’t.
Ah, crud! Thanks for the correction. I knew I should’ve written out the units. That was the best tip from my HS Physics teacher, I think. “Write out the units, make sure everything cancels so that your answer’s units are what you wanted, and the math should pretty much work out.” That’s what I get for not keeping those good homework habits!
Yeah, I noticed the Indiana flag as well, so assumed it happened there and not Kansas.
I should have said it likely happened at 4pm CST instead of 5pm EST (which is the same thing), but what good is mentioning the Eastern time zone when the poster is in the Central one?
I need more coffee too.
In fact, I haven’t even made any yet.
:O)
Momentum = m * v
Energy = ½ (m * v2)
Great, thanks for the link.
Actually, your crash involved considerably less force than a “130 mph” crash. Not to dispute the gracious protection our Lord extended, but Mythbusters showed that a head-on collision between two identical cars going the same speed is the same as one car going that same speed into a wall that does not move or deform.
I guess your 130 mph number comes from an assumption that both vehicles were going 65 mph, with the centerlines of the vehicles matching up head-to-head. This is probably not a correct assumption.
First, this was not a “head-on” crash as most people understand that term. Although it does appear that the forces acting on your truck were mostly from front to rear, they were offset. It appears that most of the force was offset to the right side of the truck. That did a lot to reduce your injuries.
More importantly, it is clear from the damage to the Saturn that she was crossing in front of you, with the centerline of her vehicle making an angle with yours of perhaps up to 30 degrees. (I could tell you more if I saw more pictures of her vehicle.) So even if she was going 65, the speed she was moving relative to your vehicle’s center of mass was something less than that.
If your vehicle had expended all the energy of its 65mph speed at the point of impact, it would have stayed at the point of impact, as a vehicle does in a barrier crash test. Instead, it had enough energy to come off the ground and spin around. That further reduces the energy available to injure you.
Nor did the Saturn stop at the point of impact, but traveled some distance beyond, including a rollover.
Any post-collision motion is caused by energy, has to be accounted for, and cannot be part of the injury-causing mechanism. It’s not the crash that kills you, it’s the sudden stop at the end. The less sudden the stop, the less energy available to cause injury. It’s a concept called “ride-down,” and it’s why you wear your seat belt.
Again, not to diminish this tragedy or the good news of your survival. Prayers up for all involved.
Thank God you are ok FRiend.
Don't let her sit with her feet on the dash. Seat belts work only when you are in a proper seated position. When misused, seatbelts will cause more harm than no seat belts.
Prayers for all involved.
I’m so glad you are ok! I was hit head-on by a drunk driver in 2007, and my back is still tweaked sometimes. Take care of yourself!
A lesson the engineers of the Mars Probe that did a nose dive into the planet should have heeded since one group was working in KPH and the other in MPH.
Not having a three-point belt in this crash would have been very bad, and don't assume that your airbags will protect the center occupant. The center front seat should be the last seat filled. If you really love her, have her sit in the seat with a three point belt.
M = 7800 lb * 0.45 kg/lb = 3510 kg
V = 65 mi/hr * 1.6 km / mi = 104 km / hr
Momentum = m * v = 465,040 kg·km/hr
Energy = ½ (m * v2) = 0.5 * 3510 kg * 1000 g / kg * (104 mi / hr * 160 934.4 cm / mi * 1/3600 sec / hr)^2...
1,755,000 * 4649.216^2
1,755,000 * 21615209.414656 = 37,934,692,522,721.28 ergs (g·cm2/s2)
Trillions of ergs? Low confidence in that answer. Did I get it right?
Nice analysis.
“The force that you and your car experienced would be as if you hit a stationary object at 65 mph.”
It wasn’t exactly a head-on collision, and the two vehicles were not the same mass, but if it were a head-on collision between two vehicles of the same mass, and they were both traveling at 65 mph, then I think your idea is correct that it would be essentially the same as driving a vehicle into an immoveable concrete barrier at 65 mph. I think it would also be the same as driving one vehicle head-on into the other at 130 mph if the other vehicle was stationary.
Thank you, and I certainly took it in the spirit in which it was intended. Good to have interesting and pertinent things to read and learn while waiting to feel better. (I really need to find another good author to obsess over!)
Here’s another article I just found:
1 killed in Sumner County accident
BY HURST LAVIANA
The Wichita Eagle
One person was killed and another injured this afternoon in a near-head-on collision on K-42 just south of the Sedgwick County line.
Sumner County sheriff’s Capt. Mike Yoder said the accident occurred when an eastbound pickup collided with a westbound Saturn.
Witnesses said it appeared that the driver of the Saturn was having trouble staying in a single lane of traffic before the accident occurred, Yoder said.
The driver of the Saturn was pronounced dead at the scene, Yoder said, while the pickup driver suffered minor injuries. The Kansas Highway Patrol is investigating the accident.
I survived a highway head-on on a motorcycle in 1972. I was going probably 50 and the car that came over into my lane was traveling “fast” according to witnesses. I was DOA at Shands teaching hospital, tagged and pushed out of the way because the ER was full of the victims of two bad auto wrecks. Two interns saw the dead guy on a gurney and decided to practice life saving techniques and now I am on FR. I have no sympathy for folks who say they never want to go to a teaching hospital lest they be subject to mere students.
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