That's not off topic, it's all about walking on water, isn't it?
False vacuum, that mythbusters episode sounds a bit sketchy to me.
Been busy but finally thought about this question a little more.
One example which may show that running could cause a footfall to land harder than walking is that joggers and runners have more knee problems than walkers do, even if they run relatively short distances.
Running/basketball shoes have more shock-absorbing support (or are at least are purported to have) than regular tennis shoes.
This may have to do, in a way, with weight dispersion (or force distribution?) because at the point in time when the left or the right foot lands (while running), more of the weight (or force) is concentrated in that (left or right) leg and foot than in the other leg (and than it would be if walking).
Additionally, I suppose the possibility of some kind of oddball reaction occurring in the ice can be factored in (as in Dr. Kaku's description of a diamond breaking when its nodal point is hit) when running as opposed to walking. In other words, the object being struck may have a disproportionate reaction.
So, in this particular case, you are not just looking at the amount of force, you may have to also look at inestimable reactions (the degree of which may be unpredictable) in the object being struck.
On the other hand, how hard a person hits something/how badly it breaks (in this case, ice) might actually have more to do with their strength than with their weight.
(Of course in this next example, I'm assuming the person is
trying to hit the ice harder rather than trying
not to break the ice):
Weightlifter #1 weighs 175 pounds and can do 300-pound legpresses.
Weightlifter #2 also weighs 175 pounds but can do 400-pound legpresses.
Which person could kick a better hole through ice? I'd say #2.
So, at least in this case, the person's weight has nothing to do with how fast and how hard of a hole he could make if he were trying.
There is no doubt that length of time that the foot remains on the ice makes a difference but it's probably not the
sole (for lurch) factor.
It would seem that there are many considerations- some which may produce only slight variations in estimation and perhaps others that could produce considerable difference in outcome.
I'm just throwing out ideas. Gadzooks, what a headache issues like this must be. Glad I didn't take engineering.
Speaking of which, maybe a lurking engineering geek will be kind enough to state the textbook terms and outcomes (the predictable ones) for our sprinter and our walker.
Or we could HallsofIvy's advice and tie a rope and a flotational device around Lurch.
Hm. I shouldn't skim the posts, I missed reading a few of them.
Okay, here's comments to several:
(#2)False Vacuum,
Yes, the second paragraph (as many have stated) is more a result of "getting the hell out of dodge" quicker. Before the ice has time to crack. Soggy feet, however, may be another issue. :-D
(#4)da_willem,
There are a lot of factors that determine whether the person falls through. The two main ones are, of course, how big of a hole his foot creates and, secondly, how strong the next patch of ice he lands on is.
He may only come out of it with soggy feet (if the ice breaks real slowly) but he's also taking a big chance when he stomps on ice that the area that breaks will be too large for him to escape from.
I think I would prefer the idea of laying down on the ice. Not just because of the weight dispersion factor that has been mentioned in another post but also, think of this:
If there's the possibility that you're going to go under
anyway, you might as well be laying down. For one thing, you won't fall as hard and as far underwater as you would have if you were standing up when you fell through and you will still have a better shot at maintaining your bearings so that you might be able to lift yourself up onto the (hopefully) stronger ice that surrounds the hole.
The disadvantage to laying down is, of course, that you can't move around very efficiently. Unless you're being chased by a polar bear, though, I'd think it would be better to escape mother nature and Newton's laws slowly and patiently.
(#5)false vacuum,
Strength is another consideration. It would seem that someone with stronger legs than another person would run harder (land harder), whether or not their weight was the same. (sort of like a Holyfield punch as compared to a Jim Carrey punch)
Unless the stronger-legged person were somehow able to be more careful and tread lightly (if possible). You would surely think that there could be some degree of control involved.
(#11)Lurch,
Your post remind me of Wiley Coyote. When he's suspended in mid-air, he doesn't fall until he looks down and realizes he's not standing on the cliff anymore.
I guess the writer thought he'd use a little of the Shrodinger's Cat interpretation.
(#12)false vacuum,
The ladder might serve an additional purpose (other than just weight dispension) by anchoring it above one (or more) stronger patches of ice. The theory being that the stronger patches might still support the entire ladder even if part of the ladder is covering weak patches.
I think I'd use a wooden one. Aluminum's lightweight but I know that wood might float.
Haven't read Muon's post yet, though.
