Quote:
Originally Posted by theclencher
Ooooo, a big crowbar! That packs what, .000001% of the force of even a 5 mph impact?.

Um... Nope. And really, no need to be so rude. And if you really think it's such pittance? Go wail on your front bumper with a crowbar. I mean, it's only .0000002% of what a 2.5mph impact is, right?
A bit of math... My quick research on average speed brought up a lot on golfing, and was showing the average driver head speed at 120 kph So, assuming a crowbar at approximately 1/3 of the length of the club, the end of the crowbar would be going at about 40 kph. (Or, about 11 meters per second)
A quick bit of research found a lot of crowbars at between 810 kg (for steel), and assuming about 50% of the weight to be what's "behind the blow", let's just pick 4kg.
Kinetic energy is .5(mass x velocity^2) (in joules)
so, swung crowbar has about 240 joules behind it. (rounded down)
The car weighs about 1600 kg, and at 5mph (2.2 meters per second), it has about 3900 joules of kinetic energy. (rounded up)
It makes quite a bit of sense for the impact of the crowbar to be no more than 4 cm^2. (crowbars are usually about 2cm wide, and the impacted portion of the bumper is 2cm wide), so with 240 joules impacting 4cm^2, you have a pressure level of about 60 joules/cm^2.
The car is about 1800cm wide, and let us even assume that only 1/2 of it has an impactable bumper. that's 900cm of impaction width, and still assuming out 2cm bumper width, 1800cm^2.
3900 joules impacting 1800cm^2 comes to about 2.2 joules/cm^2. (rounded up)
Heck, let us assume that only that little ridge in the front can impact anything. A mere 30cm tall portion of the bumper. It's the leading edge of the car, and in an impact with a wall, that is all that would hit.
Still, assuming that same 2cm width that was impacted, we come up with 60cm^2. 3900 joules impacting 60cm^2 comes up with 65 joules/cm^2.
So, 60 Joules/cm^2 as the level of impact force for the crowbar on the bumper.
And 65 Joules/cm^2 for the impact force of the car hitting a wall at 5mph.
(And this is rounding down all calculations with the crowbar, and rounding up all calculations with the car)
Yeah. .0000001%.
Of course it is.
Edit:
Sorry for the really long winded math heavy thing, but I don't take well with people being flat out ******* level of rude in an otherwise fairly calm discussion.
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