An interesting question arose as my friends and I were playing Dagorhir the other day. My one friend (Alex) said that two swords hitting each other at x speed would produce as much force as one sword hitting a stationary one at x speed, and my other friend (Bob) said that was bunk.
Now, I was called in, being a fan of physics and the most literate in the subject (I think), to settle the argument. Turns out that Alex had been quoting an experiment from Mythbusters (I hunted it down; it’s specifically the episode entitled “Mythssion Control”) to prove his point. In it, they apparently have a test where they run two clay blocks, and then two cars, into each other and then into a wall to demonstrate how the forces are the same by measuring deformation of the clay or cars. Bob cleverly pointed out, however, that the test in which the clay hit the wall was misleading because the clay, and the car, deformed while the wall did not. When the clay are run into each other, they both deform to an equal extent. To me, this is an example of elastic vs. inelastic collisions. Since our swords are more closely rigid bodies than lumps of clay under the power of our swings, I concluded the forces experienced by the swords are doubled with the collision in which both are moving.
My question is this: have I missed anything?