sgtrock21:
Did you ever flip tiddlywinks? Not sure the same thing applies…
If the manhole cover got slightly dislodged so it was sitting over the hole with about an inch or two of gap, the (rear) wheel of a vehicle could cause it to flip as it pivoted around the two points where the cover touched the manhole. If the gap were towards the front of the vehicle, it could clear the vehicle and flip upwards. At least that is my theory.
Whether one can understand it or not, it happened. And we can theorize forever and only the guys who investigated the accident will ever know the truth… and I seriously doubt if that investigative report will ever be released to the public. Physics will do what it will. The challenge then is understanding what it did.
My own theory is centered around a collapsing substructure and broken seating ring. I’ve seen that more than once. But I’ll never really know either.
The comment on gravity being defeated is interesting. One of the things engineers learn (discover?) is that you cannot defeat physical forces… you need to learn to USE physics to OVERCOME physical forces. I know I’m quibbling on a word, but it’s an important point to understand. Engineers learn to use physics, not to defeat it. In the case involved, the solution to what happened isn’t how gravity was defeated, it’s how inertia manifested itself.
Personally, I would love to see the official investigation results. But I doubt if it will ever be published.
Did not hear about the boulder on the highway, but if you are in WI be sure to see the "Rock In The House"
http://www.roadsideamerica.com/story/2243
Did pressure from methane gas ignition blow the cover up?
Can’t imagine any vehicle’s weight/speed exerting enough leverage to flip theavy personhole cover up to windshield height.
If under the vehicle, it would strike the underside of the vehicle.
If rolled on at the side of the vehicle, there is nothing directly above for it to hit.
We worry about rocks and deer coming through the windshield.
I have a deep respect for physics. Here in the midwest, there has been more than once that a tornado has drilled a piece of straw into a tree or wall, as crazy as that sounds. Still I have trouble envisioning the flying cover.