Movie Clip - Titan A.E.

Spiderman: Centripetal Acceleration and Goat Spiderwebs?

"The Physics of Superheroes" is honestly really interesting just for the amount of stuff you can learn while talking about something that is genuinely interesting. Although, if you do find yourself reading this for fun you have reached ultimate nerd status. Welcome to the club.

One of the most interesting bits that I found in the book pertains to spiderman. Particularly, his webbing and ability to swing from building to building. The question that the author poses is, quite simply, can spiderman swing from building to building on really only spider webbing.

As it turns out, from a physics standpoint, it's totally possible. As spidey-boy is swinging amongst the skyscrapers or new york, he is experiencing a centripetal force as he is swinging even though he is not experiencing a pure acceleration in one direction. The author notes that as you swing in a semi-circle, you're constantly changing the direction of your speed. Therefore, your velocity is being changed as you swing in an arc which is technically an acceleration. 

Now, the main question is, can spidey swing in that manner without his webbing splitting apart and him falling face first into the grave next to uncle Ben. In this example, the force of the Tension of the webbing is the main force. The webbing itself is what holds spidey-guy up and it's what holds him in place in that arc. Meaning that it has to both hold his weight and provide a force to get him moving in the arc. 

The formula that the author uses is the following. 

T = mg + (mv^2)/r

m = mass of spiderman

g = gravity

v = speed of spiderman

r = radius of his arc = length of his webbing

After some quick math, and assuming that his mass is 76kg and the length of his webbing is 200 feet, we arrive at the number 300 pounds of tension. That may seem like a bit of a stretch, but, if spidey's silk is actually real spider silk, it's entirely possible. Dragline silk webbing is 5 times stronger than steel cable per pound than steel cable and as elastic as nylon. And, furthermore, spiders can often control proteins in their bodies to modify the tensile strength of the cable. Therefore, if Spidey can do that, then he can practically make his webbing unbreakable.

The author goes on to talk about the research going on where scientists are trying to "farm" this material. Spiders are territorial and don't produce much webbing so it wouldn't be easy to farm them conventionally. However, some researchers have found a way to splice spider DNA into goats so that the proteins in the webbing can be found in the goat's milk and then made into a weaker than normal webbing. Although this webbing is weaker than it could be, it's still stronger than the steel cable as mentioned before. 

This may sound weird, but the engineering applications are practically endless. It would be five times more effective than kevlar at stopping bullets. The high tensile strength of spider silk means, in theory, if we could make a rope of it that was 1 centimeter in diameter, it would be able to hold 8 tons before breaking. 

So, the idea that spiderman can swing from a rooftop? Totally possible. 

Also, they should've made Uncle Ben a goat farmer or something. Would be much more fitting I think.