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Encyclopedia > Center of percussion

The center of percussion is the point on a bat, racquet, sword or other long thin object where a perpendicular impact will produce translational and rotational forces which perfectly cancel each other out at some given pivot point. The center of percussion may or may not be the "Sweet spot" depending on the pivot point chosen. Squash racquet and ball Racquetball racquet and ball Tennis racquets and balls A racquet (or racket) is a sports implement consisting of a handled frame with an open hoop across which a network of cord is stretched. ... Swiss longsword, 15th or 16th century Sword (from Old English sweord, cognate to Old High German swert, literally wounding tool from a Proto-Indo-European root *swer- to wound, to hurt) is a term for a long-edged, bladed weapon, consisting in its most fundamental design of a blade, usually... Perpendicular is a geometric term that may be used as a noun or adjective. ... A sweet spot is a place, often numerical as opposed to physical, where a combination of factors suggest a particularly suitable solution. ...

## Contents

Imagine a beam is suspended from a wire by a U-bolt so that it can move freely along the wire. A blow to the beam below the center of gravity will cause the beam to spin around the CoG and also cause the CoG to move away from the blow. If the blow falls above the CoP the movement of the CoG will cause the U-bolt to move away from the blow since the effect of the translational acceleration will outweigh the effect of the rotational acceleration. If the blow falls below the CoP the opposite will occur, rotational acceleration will outweigh translational acceleration and the U-bolt will move towards the blow. Only if the blow falls exactly on the CoP will the two cancel out to produce no net movement of the U-bolt.

Image File history File links Percussion. ...

## Calculating the center of percussion

In a free beam of uniform density, a force F applied at a right angle at a distance b from the center of gravity (CoG) will result in the CoG moving at a velocity V according to the relation: This article is about angles in geometry. ... This article or section may contain original research or unverified claims. ...

Where M is the mass of the beam. Similarly the torque exerted will be as per the relation: In physics, torque can be thought of informally as rotational force. Torque is commonly measured in units of newton metres; although, centiNewton Meters (cNm), Foot Pounds (Lb-Ft), Inch Pounds (Lb-In) and Inch Ounces (Oz-In) are also frequently used expressions of torque. ...

Where I is the moment of inertia around the CoG and ω is the angular momentum. Moment of inertia (SI unit kilogram metre squared kg m2) quantifies the rotational inertia of an object, i. ... In physics the angular momentum of an object with respect to a reference point is a measure for the extent to which, and the direction in which, the object rotates about the reference point. ...

For any point P on the opposite side of the CoG from the point of impact:

v = VAω

Where A is the distance of P from the CoG and v is the velocity of point P. Hence:

v is then given by:

The axis of rotation is situated where v = 0 and the corresponding center of percussion is at distance b from the CoG where:

and for a beam of length L the moment of inertia around the CoG is:

(see moment of inertia for proof) Moment of inertia (SI unit kilogram metre squared kg m2) quantifies the rotational inertia of an object, i. ...

## Relation to the sweet spot

The sweet spot on a baseball bat is generally defined as the point at which the impact feels best to the batter (it is also occasionally defined as the point at which the maximum velocity is imparted to the ball, but this may not be the same point). A sweet spot is a place, often numerical as opposed to physical, where a combination of factors suggest a particularly suitable solution. ... Baseball is a team sport in which a player on one team (the pitcher) attempts to throw a hard, fist-sized ball at a player on the other team (the batter), who attempts to hit the baseball with a tapered, smooth, cylindrical bat that can be made out of either... The velocity of an object is simply its speed in a particular direction. ...

Although it has long been believed the center of percussion and the sweet spot are the same, recent practical observations have indicated that the point many batters feel is "sweetest" corresponds to a pivot point not in the handle of the bat but beyond the end of the bat. The reality of, and explanation for, this anomaly are currently areas of active research.

## Application to swordmaking

The center of percussion, or sweet spot, of a sword is the point on the blade where cutting is most effective. It is also the division between the weak and middle sections of the blade. A sweet spot is a place, often numerical as opposed to physical, where a combination of factors suggest a particularly suitable solution. ... Swiss longsword, 15th or 16th century Sword (from Old English sweord, cognate to Old High German swert, literally wounding tool from a Proto-Indo-European root *swer- to wound, to hurt) is a term for a long-edged, bladed weapon, consisting in its most fundamental design of a blade, usually... A blade is the flat part of a bladed tool or weapon that (usually) has a cutting edge and/or pointed end typically made of a metal, such as steel used to cut, stab, slice, throw, thrust, or strike. ...

Like any solid object, a sword vibrates when impacted (such as during cutting). In a sword, such vibrational waves are typically almost imperceptible. Every wave expressed by a solid object has rotational nodes where the wave reverses at either end of the object. On a properly-balanced sword, one node is in the tang of the sword (inside the hilt), ideally directly under the primary hand. The other is the center of percussion. On such a “harmonically balanced” sword, this means that a solid blow can be delivered without causing discomfort in the hands. The center of percussion of a sword is related to its center of balance, and both can be moved by employing a heavier pommel or changing the mass distribution of the blade. A wave is a disturbance that propagates through space, often transferring energy. ... Rotation of a plane, seen as the rotation of the terrain relative to the plane (exposure time 1. ... Tang could refer to: Tang Dynasty of China Tang (Shang dynasty ruler) Transliteration of Chinese family names such as å”,æ¹¯,é„§,é‚“,æ»• Tang Clan of Hong Kong, the first inhabitants to leave China and settle in Hong Kong. ... See also: Hilt (band) and Peter Hilt The hilt of a sword is its handle, consisting of a guard, grip and pommel. ...

So-called “blade harmonics” are a commonly misunderstood concept, especially by sword enthusiasts and their internet communities. The common belief is that a sword must be “harmonically balanced” in order to cut properly, because the vibrations would otherwise interrupt the line and power of the cut. As explained above, this proposition is false: the vibrations caused by a sword cut are almost unnoticeable except as a mild stinging to the hands even in blades that lack this quality. It has also been demonstrated that the object the sword cuts through serves to further reduce the intensity of any vibration, making it even less noticeable. A virtual community is a group whose members are connected by means of information technologies, typically the Internet. ...

Many experts speculate that harmonic balance is merely a byproduct of proper construction and balancing, rather than an intentional quality added to weapons. Unfortunately, some sword vendors advertise "secret techniques" of harmonic balancing in an attempt to "prove" the superiority of their products. This only serves to amplify the false impressions of the value of harmonic balance by seeming to lend them legitimacy.

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