1. 2011

    Scattering a bullet off an RPG

    Yep, that’s right, a rocket-propelled grenade finally made its way on Mythbusters! Personally I’m surprised it took them so long…

    Anyway, let’s not get distracted from the science by cool explosions just yet. On last week’s season premiere of Mythbusters, Kari, Tory, and Grant tested a myth based on a scene in RED in which two characters are facing off, one (the hero) with a revolver and the other (the villain) with an RPG launcher. In the movie, they both shoot at the same time, the bullet hits the RPG in midair and detonates it, and the resulting explosion kills the villain. Now, in the show, this myth was busted on several counts:

    • RPGs don’t even arm until about 60 feet after launch, about \(\frac{3}{4}\) of the way to the target and long after this one would have been hit by the bullet
    • When an RPG explodes, it sends balls of molten copper flying forward, which wouldn’t have been stopped by the bullet
    • The distance at which the explosion would have taken place, 16 feet from the villain, is quite survivable

    Unfortunately, they didn’t test what I thought was the most …

  2. 2009

    Unarmed and unharmed

    This is one of those really cool things that I’ve often wondered about: can you really shoot a gun out of an outlaw’s hand? Last week on Mythbusters, Adam and Jamie decided to test it out. Sure, it’s not the kind of thing you’d think would be easy (or safe) — unless you have access to that classic Mythbusters creativity. Their first idea involved a Velcro-like gripping arm to hold the gun, and although it may not be clear just how exactly that compares to a real hand, they obtained some interesting results from comparing the different gripping positions.

    Anyone who’s ever tried to pry an object out of somebody’s hand knows that the easiest way to do it is to twist it to apply stress on the thumb, the weakest point of the grip — not just to hit it as hard as possible. And whenever an object is twisting or rotating, the operational physical principle is torque, the rotational analogue of force. Torque can be calculated from the formula

    $$\vec{\tau} = \vec{r}\times\vec{F}$$

    but in most simple cases, we can identify an axis of rotation and then calculate the torque around …