The physics of Spiderman
This is the kind of thing you'll see over at Insultingly Stupid Movie Physics:
A web strand would probably need to be at least 0.5 cm in diameter to support Spider-Man's web-swinging antics. If such a strand were 100 meters long, it would have a volume of 0.00196 m3 compared to Spider-Man's estimated volume of 0.0726 m3. Spider-Man will lose 2.7% of his volume every time he shoots a 100-meter-long web. Web swinging a mere kilometer of horizontal distance would use up 38% of his body volume (assuming his web makes a 45° angle with the vertical at the beginning and end of each swing and each web is 100 meters long). He would be skeletal by the time he arrived and would have to eat huge volumes of food to compensate.
On the other Hand, The Road to Perdition had a high physics realism rating. Go figure.