Throwing Knife Physics: Why Blade End Hits More Often

  • Context: Undergrad 
  • Thread starter Thread starter Aditya3003
  • Start date Start date
  • Tags Tags
    Knife Physics
Click For Summary

Discussion Overview

The discussion centers on the physics of throwing knives, specifically why the blade end tends to hit the target more often than the grip end. Participants explore concepts related to angular velocity, center of mass, and the mechanics of knife throwing, including factors such as distance, rotation, and thrower skill.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the knife's blade end hits more often due to the center of mass being closer to the point end, affecting its rotation and impact with the target.
  • Another participant notes that timing and skill play a significant role, as poor execution can lead to the handle hitting the target instead of the blade.
  • A participant references general principles of knife throwing, including the importance of accuracy, distance, and the number of rotations, while mentioning different throwing techniques (spin vs. no-spin).
  • One participant shares personal experience, indicating that the blade does not always hit the target and emphasizes the need for a specific distance-to-rotation ratio for successful throws.

Areas of Agreement / Disagreement

Participants express differing views on the mechanics of knife throwing, particularly regarding the factors influencing whether the blade or handle hits the target. There is no consensus on a singular explanation, as multiple factors and personal experiences are discussed.

Contextual Notes

Some claims depend on the specific definitions of terms like "center of mass" and "rotation," and there are unresolved aspects regarding the precise mechanics of knife throwing and the influence of thrower skill.

Who May Find This Useful

Individuals interested in the physics of sports, mechanics of throwing techniques, or those looking to improve their knife throwing skills may find this discussion relevant.

Aditya3003
Messages
7
Reaction score
0
When a throwing knife is thrown why does it only hit its blade end ( not the grip end)? The knife has been imparted with a spin and there is a 50:50 probability that its blade end will hit (actually a bit less).
It would be better if you explain assuming the blade's CM has velocity 'v' and is imparted with an angular velocity ω and its target is at distance 'd' if the explanation is complicated.
I think it is because the knife only spins once and the brain automatically calculates the angular velocity which needs to be imparted.
 
Physics news on Phys.org
My understanding is that this happens primarily because the center of mass of the knife is towards the point end. As it moves right up close to the target, either the last rotation causes it to stick (by the point), OR it causes the handle to not hit the target and there is then another revolution that embeds the point.

EDIT: and by the way, they DON'T always stick by the point. Bad timing can occur and they bounce off, so part of the explanation is the skill of the thrower.
 
Wikipedia- http://en.wikipedia.org/wiki/Knife_throwing#Basic_principles
Knife throwing, whether in a martial or sport application, involves the same basic principles of mechanics. The objective in each case is for the point to stick into the target with a sufficient amount of force. For this to be successful, accuracy, distance, number of rotations and placement of the body all must be taken into account unless a no-spin technique is employed by the thrower (there are spin and no-spin throwing techniques). If the thrower uses a spin technique, the knife will rotate during flight.[1] This means that the thrower, assuming he is throwing the same way every time, must either choose a specific distance for each type of throw or, more practically, make slight adjustments to placement of the knife in the hand as well as angle of release and rotation of the wrist. Variations in throw technique can allow great accuracy and range. Throwers may also need to adjust for throwing off-center, around corners, and while running.
 
I used to play with throwing knives a lot last summer and the blade doesn't always hit your target. I've gotten the handle stuck in a tree before. You have to learn how to throw them. There is a certain distance:rotation ratio you have to follow
 
 
Last edited by a moderator:
Around corners? Cool!
 

Similar threads

Is Throwing a Knife with No Spin Actually More Effective?
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Ceiling fan and impact force on the blades
  • · Replies 11 ·
Replies
11
Views
2K
High School The physics of flywheel launchers (like tennis ball shooters)
  • · Replies 60 ·
3
Replies
60
Views
7K
Graduate Modeling the damping of a physical rigid pendulum
  • · Replies 1 ·
Replies
1
Views
2K
High School Throw Snowball from Car for Maximum Force: Physics Explained
  • · Replies 5 ·
Replies
5
Views
2K
Graduate Why does the Split-finger baseball pitch break?
  • · Replies 8 ·
Replies
8
Views
8K
Undergrad Physics of Baseball: Understanding Angular Velocity
  • · Replies 4 ·
Replies
4
Views
3K
How Does Wind Turbine Blade Length Affect Power Output?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Toppling a Hemisphere: Solving for Kinetic Energy in a Delicate Collision
  • · Replies 2 ·
Replies
2
Views
2K
Graduate Why does atmosphere rotate w/ constant angular velocity?
  • · Replies 34 ·
2
Replies
34
Views
8K