Good movie.
Back of the envelope calculation: When Spidey's alerted by police sirens to swing into ACTION!, we routinely see him swinging past the police cars at roughly twice their speed. Figure 40 mph in Manhattan is a likely speed for a cop car, so Petey's swinging at about 40 meters per second.
Randomly guessing, his web lines look to be maybe fifteen stories long; call it 50 meters.
So the acceleration he's feeling at the bottom of his swing is v^2/r, or 32 m/sec^2, about three gravities' worth of force. That's a lot for a human, but not for Spidey, so his swings aren't terribly implausible.
But now look at his web lines. When he throws one, it travels 50 meters and attaches in a fraction of a second, even when Peter is going full speed in the other direction. Peter ejects web fluid--out of ducts in his wrists, remember--on the order of 200 meters per second--four hundred miles per hour. And he can do this repeatedly, producing large volumes of material and varying the shape of the stream. How's that for a metaphor for ejaculation?
Man of Chitin, Woman of Kleenex?
So Joe Criminal, running down the street with his ill-gotten gains, takes a 400MPH splat of spider-spooge in the small of his back. Does he live?
So, Spidey is going all out down broadway and his next swing requires him to hit an upper window on the Reuters building (3 Times Square). Does the window break? If not, does it get pulled away from the building as Spidey swings through mid-town?
If Peter is careless enough to aim at a window, yes, I figure most windows are not strong enough to take three times the weight of an adult human male, even a scrawny one like Parker. Either the window or the frame will break.
Peter mostly attaches to the stone of buildings' facades. In the movie, in fact, we see that the tensile strength of the web and the adhesive strength of the attachment point is stronger than the stone's physical integrity, as Peter destroys some walls trying to use his web line to slow down a runaway train.
Also in the movie, in fact, Peter does use (or appears to use) blobs of spider-goo as improvised throwing weapons. Getting a blob, even a light one, in the face at 400 mph would crimp your style all right. Though it would probably be at least as effective, tactically, to use sticky-net ejaculate to blind people.
Dude, you can vary the shape of the stream? Wow.
You are correct about the acceleration at the bottom of the arc. If you believe in "spider-strength", then it's not a problem.
And if pete's webbing is as strong as real spider silk, then the accelearyion could be much more before you have to worry about it snapping. Real drag line silk has a tensile strength five time greater than steel cable, pound for pound, as is stretchier than nylon.
Your Friendly Neighborhood Physics Professor,
Jim
Presumably, Spidey can vary the speed at which the webbing is ejected?
I'll add for the benefit of people coming in from Tagline, that the "dick joke" arises from the fact that Spidey's power failures, particularly with respect to his web-shooters, are clearly meant to suggest impotence. He doesn't go so far as to say "This has never happened to me before", but he goes right up to that point.
I was wondering how fast you could get along by this project and swing technique. Eg you're 50 metres high project 40 metres ahead and then swing (with 10m safety margin) -- how long does it take to get the same height the other side of the arc.
There's a simple formula (which I forgotten) for the speed of pendulums with a small arc (not valid as is it approaches 180 degrees) -- but what is the optimal arc for speed?
Also, this issue about how much thread he ejects. I think a gallon would go quite a long way for swinging on (imagine the length of a gallon of string) or even to tie up the odd super villain -- but surely not for stopping a train.
How does he replenish I wonder ... wolf down a gallon of water and a couple of pounds of sugar ... or perhaps he gobbles up flies as he swings through the air with swallow-like grace ...
and another thing ... how strong is spiderman?
In movie 1, he supports a cable car while the cable is nearly horizontal -- which is much harder than if the cable is vertical. He must have at least 50 tons pull in one arm ...
So, say with both legs he can thrust downwards with about 200 tons, how high can he jump?
If he weighed 200 lbs (.1 tons) he could accelerate at 2000g ... and jump 1000 to 2000 times the length of his legs.
You can work out the rest for yourself