The Physics of Knife Throwing

Question: What kinds of knives do you throw?

David Adamovich: That’s a typical throwing knife.  It’s a 14-inch knife, about an eighth of an inch thick, it weighs about 12 ounces.  A good throwing knife will be at least that size, between 12 ounces and 14 ounces, at the most one pound, 16 ounces.  It’s got a good piece of steel in your hand, a nice point, and that’s what sticks in the wood.  So whether or not I’m throwing knives, tomahawks, axes, or Bowie Knife, the process is always the same.

Question: What are the physics of knife-throwing?

David Adamovich: The physics of throwing a knife is the same every time, whether I’m throwing by the handle, or the blade.  If it’s a blade throw, it’s called a half-spin and it starts back here, right back by my shoulder, and I bring my arm forward and aim it right to where I want it to go.  Now in that position right there, when the knife is actually like this, in the air – I’m sorry, as my hand gets into that position, it slides off, the knife makes a quarter turn, which doesn’t count.  And now it needs to make another half turn to get that point to the board so it does this in the air, and then finally gets to the board and sticks.  

If I were throwing it for a full spin, I would hold it by the handle, I’d start back here, right behind my shoulder, the arm comes forward and straight out pointing to where I want it to go.  And then as the hand passes through this position, it slides out, makes a quarter turn, that doesn’t count, and now that point had to make one more full turn to get to the board, which is over there.  So, it will go like this in the air, and get there point first.  

The speed of the knife has always been a contention among knife throwers.  I’ve checked it with radar guns, I’ve checked it with 60-frames-per-second videography, it always works out the same.  The knife is going through the air between 26 and 30 miles per hour.  So, from where I’m standing to get to the board is somewhere just under two-tenths of a second.  

Question:
Do you have to be a certain distance from your target?

David Adamovich: When I first started performing, I devised the act for almost everything at a full spin.  So all my items were thrown from the handle and I was out about 12 feet.  But as I was going to different venues, I found out I didn’t have the space on stage to do a full spin throw, plus the distance to the board to the back of the stage.  The stages just don’t allow it. So I revised the whole act to be half-spin, all the knives, and that’s at about seven feet from the board.

So when I’m throwing the big things, like axes and tomahawks, I have to go out to about 12 feet because I’m holding them from the handle versus the blade.

Recorded on July 15, 2010

Interviewed by Max Miller

The Great Throwdini shows us his favorite projectiles and explains the mechanics of making them always hit the right spot.

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