Punching and
Getting Punched
Even in the sport of boxing, physics
can be seen in all aspects of the game. However, we will be looking at how
physics can help a boxer in both throwing a punch, and taking a hit to the
face!
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Starting the
Punch
When the fighter has his hands in their initial
“ready” positions, his fists have potential energy originating from muscles and
various bodily functions. As soon as the boxer starts to move his shoulders and
arms and eventually the fists, his/her potential energy is being converted into
kinetic energy.
Kinetic energy is calculated by using the formula: Kinetic Energy = (1/2)mv^2
where
m is the mass of the object, in this case the arm, fist, and boxing glove, and
v is the velocity of the object.
Contact with the
Face and Aftermath
The
fist has its maximum velocity when it hits something. This collision causes the
fist to slow down, and eventually when the fighter begins applying a force to
retract his arm, the fist stops and returns to the fighter.
This speed is calculated using; Velocity = Distance / Time
As
you can see, there are two ways to make a fist go faster. By lengthening the
distance or shortening the time. The distance can be lengthened to a maximum of
the fighter’s arm length, but the time will depend on training, and the
acceleration (a=v/t) of the arm.
But what is the advantage to a
“faster” punch? We can investigate this by taking a look at the concepts of
momentum and impulse.
Momentum can be seen as an object’s tendency to resist change in acceleration and its formula is: Momentum (P) = Mass * Velocity
An impulse is the change in momentum of a certain object, and uses the formula: Impulse = Force * Time
Now
what does this have to do with boxing? Well, this becomes more evident when
looking at the punch in steps:
1.
Before the fist
makes contact with the face, it has a certain momentum, and a stationary head
would have zero momentum.
2.
During the
contact, there is a transfer of momentum from the fist and arm to the head of
the opponent.
3.
Although
momentum is conserved when looking at both boxers, just looking at the person
taking hit, his/her momentum has changed from zero, to what ever momentum was
transferred from the fist.
To
return to the question of why a faster punch can be more effective is because
with the mass of the fist being constant, by increasing velocity, the momentum
that the punch carries is larger, hence, but change in momentum (impulse) that
the opponent’s head experiences increases.
During
contact, the boxer taking the hit would experience the same impulse whether
his/her head is moving towards the punch, or moving away from it. It is
important to understand that this doesn’t mean that the boxer would feel the
same impulse if he/she was moving towards the punch before the fist made
contact with his/her face, it must be after contact is made. Even though the
impulse, or change in momentum, experienced would be the same for both cases,
by moving the head away
from the punch increases the time interval in which the “damage” takes place,
meaning the force experienced from taking the punch will be reduced. Since it
only takes a boxer a fraction of a second to throw a punch, a small reduction
in the time interval can produce large results.
As you can see, the simple basic
punching in boxing involves many physics concepts. By knowing these concepts,
the boxers can know what aspects of their offense and defensive abilities need
training, and we can have a more scientific approach to the sport.
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