SSS 2008-03-31（在线收听）

This is Scientific American's 60-Second Science, I am Steve Mirsky, got a minute?
 

You are pulling the tape off the roll and it starts to tear, or you are moving wallpaper and it refuses to strip off in strips or in what may be the most infuriating case, literally, you are trying to unwrap a CD or DVD and you are confronted with shards of plastic everywhere. Well, the universe has truly conspired against you. Because when it comes to tearing these layers, the laws of physics now show that that’s just the way it is. Physicists address the so-called wallpaper problem in the March 30th online edition of the journal Nature Materials. What happens is that when you tear things, you get triangles. Because of three properties of the adhesive materials being torn: the stiffness, the strength of the adhesion and how tough the material is to rip. When you pull on the strip, energy builds up where the tape or coating is still attached to the surface below. That energy can get released in two ways by unpeeling from the surface which you want, or by becoming narrower, ultimately making those annoying little triangles.

Thanks for the minute for Scientific American's 60-Second Science, I am Steve Mirsky.