Got a question for any knife throwers

[Shannon Davidson]

Hello, My name is Shannon Davidson, and I am an urban/epic fantasy writer. I'm currently working on a scene in my novel where one of my characters is trying to teach a young man how to hit a high target (15 feet) with throwing knives. The kid can do it at eye level, but doesn't seem to be able to judge the throw at an elevated height. (Yes, there's a reason he has to do it high).

His mentor claims that nothing is different; the rotation is the same, the distance is the same, the technique is the same, etc. But I don't think that's right. If a target were raised to 15 feet high instead of at eye level, how would you make the adjustment? If it's higher, I believe there would be a greater distance to the target. Correct? If so, how do you compensate?

(Pretty sure this is one of those geometry/algebra problems my math teacher warned me about.)

Thanks for any thoughts

 

[A. Brett Schaller]

When shooting from or to a higher elevation, there is a tendency to shoot high. This is because you have a natural tendency to compensate for the projectile (be it a bullet, arrow, or thrown knife) dropping due to gravity over the distance to the target. But gravity acts over the horizontal distance to the target, not the linear distance, which is longer than the horizontal distance if the thrower/shooter and the target are at different elevations. Blackie Collins deals with this in his book Knife Throwing: Sport, Survival, Defense. This book is well worth getting if you want to incorporate knife throwing into your fiction.

https://www.amazon.com/Knife-Throwi...Blackie+Collins&qid=1572215066&s=books&sr=1-3

And just for fun, here's a picture of one of my custom throwing sets:

 

[zzyzzogeton]

When shooting from or to a higher elevation, there is a tendency to shoot high. This is because you have a natural tendency to compensate for the projectile (be it a bullet, arrow, or thrown knife) dropping due to gravity over the distance to the target. But gravity acts over the horizontal distance to the target, not the linear distance, which is longer than the horizontal distance if the thrower/shooter and the target are at different elevations. Blackie Collins deals with this in his book Knife Throwing: Sport, Survival, Defense. This book is well worth getting if you want to incorporate knife throwing into your fiction.

https://www.amazon.com/Knife-Throwi...Blackie+Collins&qid=1572215066&s=books&sr=1-3

Well, kinda.

Gravity works on an object over time, not distance. As long as an object is not in contact with the ground, gravity works to pull it down to the ground. The longer the object is flying through the air, the longer gravity has to work on it.

Two objects dropped from the same height hit the ground at the same time.

If you throw a knife from a height of 5 feet, at a target also set at 5 feet, gravity works on pulling it downward during the flight to the target. The time of flight dictates how much elevation must be added into the calculations to compensate for the downward drop during the flight.

Let's now raise the target 15 feet further up. (Aside - I realize the original question deals with a target at 15 feet but I am using raising it 15 feet to make the math simpler.)

If the thrower is at 15 feet from the target and the target is 15 feet above the thrower's shoulder, this forms an right triangle, where the 2 legs are 15 feet long, resulting in a hypotenuse with a length of 21+ feet from release point to target.

Now a thrown knife travels at a much higher speed than what I use here, but again I am making the math simpler.

If the knife is flying at a speed of 15 feet per second, then a horizontal throw will take 1 second to reach the target. A throw at the elevated target will travel a distance of 21+ feet and at 15 feet per second will take a little over 1.3 seconds to reach the target. So gravity has 1/3 of a second longer to act on the knife.

This means that, when thrown AT THE SAME SPEED, the knife traveling along the upward trajectory will fall a little further over the 15 feet of horizontal travel.

The solutions are to either thrown the knife faster, so gravity has less time to act on the knife OR throw the knife along a slightly more elevated trajectory so that when it walls a little further, it still hits at the desired impact point.

 

[numbersman]

Don't forget that the knife will travel in a parabolic path, not a straight line. (Technically, the center of mass of the knife, which the knife is rotating around will travel in a parabola.) High school physics, assuming you neglect air resistance, will tell you how long that path is.

 

[ErebusTX]

Hello, My name is Shannon Davidson, and I am an urban/epic fantasy writer. I'm currently working on a scene in my novel where one of my characters is trying to teach a young man how to hit a high target (15 feet) with throwing knives. The kid can do it at eye level, but doesn't seem to be able to judge the throw at an elevated height. (Yes, there's a reason he has to do it high).

His mentor claims that nothing is different; the rotation is the same, the distance is the same, the technique is the same, etc. But I don't think that's right. If a target were raised to 15 feet high instead of at eye level, how would you make the adjustment? If it's higher, I believe there would be a greater distance to the target. Correct? If so, how do you compensate?

(Pretty sure this is one of those geometry/algebra problems my math teacher warned me about.)

Thanks for any thoughts

It would probably depend on what technique he's using. If he's using standard full-spin technique, everything is about distance. If the target is higher, it's a little further away, so I would recommend either adjusting your distance or brushing the spine of the knife with his palm a little as he releases in order to slow down the rotation.