The force of an object is a product of that object's acceleration and mass. English physicist Isaac Newton introduced this fundamental identity of classical mechanics with his second law of motion, F = ma. F represents force; m represents mass; and the variable a represents acceleration. A fighter's fist or a boxer's glove when it reaches a punching bag will have a force dependent on how fast the fist or glove is speeding up and the mass of the fist or glove and arm. The unit of force is typically the Newton (N), which is one kilogram meter per second squared.
Step 1
Weigh the boxer or fighter on a bathroom scale. For example, the boxer weights 147.7 lbs.
Step 2
Multiply the boxer or fighter's weight by 0.0345 using a calculator to determine the mass of the boxer's arm. For example, 0.0345 x 67 = 2.311. The estimated mass of this boxer's arm, according to Pennsylvania State University's V. M. Zatsiorsky, is 2.3 kilograms.
Step 3
Station the boxer in front of a punching bag. Place two individuals to the right and left of the boxer. The individuals should be facing each other with a line of vision perpendicular to the direction in which the boxer will be punching. Equip one individual with a digital stopwatch and the other with an velocimeter.
Step 4
Instruct the individual holding the velocimeter to hold the device immediately to the left of the surface of the punching bag opposite the boxer. Instruct the individual holding the stopwatch to time the boxer's punch, starting the stopwatch when the boxer begins his punching movement and stopping the stopwatch when the boxer's fist strikes the punching bag.
Step 5
Instruct the boxer to punch the bag, allowing the two individuals to take their measurements. For example, the individual holding the stopwatch measures a punch time of 0.1 seconds; the individual holding the velocimeter measures a velocity of 19.0 mph.
Step 6
Multiply the punch velocity by 1.61 to convert the velocity to kilometers per hour using a calculator. For example, 19 x 1.61 = 30.59. Multiply your answer by 0.277 to convert the punch velocity to meters per second. For example, 30.59 x 0.2778 = 8.49. The boxer's punch velocity was approximately 8.49 meters per second (m/s).
Step 7
Divide your answer by the measured time of the punch. For example, the measured time of the punch was 0.1 seconds: 8.49/0.1 = 84.9. The acceleration of the boxer's fist and arm was approximately 84.9 meters per second squared (m/s^2).
Step 8
Multiply your answer by the calculated mass of the boxer's arm in kilograms. For example, 84.9 x 2.3 = 195.27. The force of this boxer's punch when it reaches the punching bag is approximately 195 kilogram meters per second squared, or 195 Newtons (N).
Things You'll Need
- Bathroom scale
- 2 assistants
- Velocimeter (see Resources)
- Stopwatch
- Calculator
References
- Texas Tech University; The Physics of Martial Arts; Brian McGonagill; 2004
- "Fundamentals of Physics"; D. Halliday, et al.; 2008
- I.U.M.A.; Biomechanical Analysis of Reverse Punch Technique in Karate & Boxing; Emeric Arus;
- "British Medical Journal"; The Damaging Punch; J. Atha, et al.; 1985
- "British Journal of Sports Medicine"; Biomechanics of the Head for Olympic Boxer Punches to the Face; T. J. Walilko, et al.; 2005
- Louisville Martial Arts Academy; Physics behind Martial Arts, Part I; Les Burton
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