How large would hail have to be to put a dent in a car hood?
I’ve seen significant dents caused by pieces about 3/4 of an inch in diameter.
In my experience (sort of a WAG, I ran for cover) it took above marble size to put dents in my truck hood.
We have some absolutely amazing hailstorms in this area. I’ve lost 2 roofs (different houses) to them, and our small plane was totaled by hail. I (being a bottom feeder) bought my wife’s van following a week of vicious hailstorms. Normally the car dealers settle with their insurance company and are willing to DEAL in the following weeks. I managed to negotiate $7000 off the price of a new van this way (just gotta live with some dents, is all).
Interesting note: A co-worker was caught out in one of our more notable hailstorms, and it destroyed every single window in their van (including the windshield). One door was damaged so severely it wouldn’t open!
How fast is the car travelling? I work in the aerospace field and there was a jet in the hangar with hail damage and I really wouldn’t have wanted to be on that plane.
IIRC the hail that beat up my rental car in Cedar Rapids was smaller than a golf ball. According to the rental agent at the airport, it’s a regular event.
Size doesn’t matter. Somebody had to say it.
What matters is the velocity of the strike.
Well, what we’re looking for here is momentum, which=mv[sup]2[/sup].
So mass does matter, maybe not size, but can we assume that all hail has a close-to-the-same density?
I don’t think so – I’ve always heard that larger hail tended to be hollow. I’ve never personally experienced larger-than-pencil-eraser sized hail myself, so I can’t verify the veracity of that.
In any case, there’s nothing beyond gravity that accellerates hail, right? So it’s got some terminal velocity. Or maybe the right downdraft can greatly increase the velocity?
I’d always wanted to study the weather – got to start with the basics, right?
Do emergency rooms in the hail storm area report large numbers of hail related injuries?
That science lesson was many years ago but IIRC, droplets of rain are caught by updrafts and elevated to an atmospheric level where they freeze, then fall and pick up another coating of fluid, are lifted again and frozen, the cycle continuing until the updrafts are not strong enough to hold the hail aloft any longer. As such, they are solid-although based on variations in temperature they can range from rock hard to softer ice/slushy.
Beyond gravity, wind could accelerate hail.
Perhaps one of the SDMB weather experts will pop in to either confirm my memory or call phooey.
(lifting wineglass)
Hail, Damage!
What?
We had hail saturday night that was a bit smaller than a golf ball. I check my car, no damage. I think anything golf ball size or greater might do some damage though. I hope I never find out. 
Storm chasing a few years ago, we were watching a storm purposely pass over us since we knew the hail wasn’t too large. It ended up being around quarter-sized (1.25" diameter), and we noticed one very small dent on the roof afterwards… The car was stationary, so I’m thinking anything under 1" is no problem for stationary objects. If you are driving though, that could be different. That said, we have driven through low-end severe hail (0.75 to 1.00" diameter) with no dent damage, and reasonable speeds, maybe 30-45 mph.
[b}danceswithcats** pretty much nailed it with the description of how hail forms.
Vis
uh. momemtum = mv
energy = 1/2 mv*v
size does matter since after a couple of thousand feet below the clouds the hail will reach terminal velocity so v will be constant. And of course (this being hail after all), above the clouds v goes positive and negative.
so damage comes from large hailstones. Small ones don’t carry enough momemtum to do much damage.
Unless one hits you right on top of the head. Boink!!! Yow!!! :eek:
Size is even more important than that, because terminal velocity will increase with size. (The ratio of mass to surface area will increase)
I don’t know. I’m aware that there a few deaths caused by the hailstorm that trashed my coworker’s van (this storm was notable even here). Also, a young man was killed in the parking lot of ‘our’ Albertson’s a few summers ago. Poor kid was trying to beat the storm to his car, caught one on his noggin. I do remember some news articles about the effect on ranchers (cows have nowhere to go during the storm). I don’t remember exactly how badly they were affected.
Marble-sized hail put dents all over our van; it was the grapefruit-sized hail that put a dent in the roof of our house.