Pendulum Periodicity Investigation:
Personal Engagement:
As an athlete, I try to immerse myself in a multitude of different sports, however, my
favourites are, Basketball, Football (soccer), Ice Hockey and Combat Sports. As a Physics
student, I draw comparisons from class to many of the sports that I do feel passionate about.
Though combat sports, highlight the major physics of the
body, and how the body can apply physical components such
as force, or pressure in order to defeat one’s opponent. The
combat sport I will be focusing on is boxing, as opposed to
wrestling or judo, which are grappling based and throwing
based sports, which account on the leverage created by the
fighters mass, hip movement, quickness and overall strength.
Boxing is a more traditional and fundamental way to assess force, as
punches are thrown directly from a straight stance, where torque is
generated from the movement of the hips, and the power is delivered
from the arm being swung. The arm can strike in many ways, from the
side like a hook, from under to up, called an uppercut, and from a
straight position like a jab or a cross (longer jab coming from the
guard hand near the fighter’s head).
Newton’s third law states that for every action, there must be an equal and opposite reaction.
Therefore meaning that from an applied force from a strike to the head of an opponent, there
must be an equal amount of force as their head bobs back and forth coming back. This can
be demonstrated and seen in speed punching bags, or arcade punching bag games. In
terms of the speed bag, the fighter would punch, and the bag would come back with an
equal amount of force, the bag continues to come back and forth as the fighter develops a
rhythm and tries their best to maintain that force and rhythm to build coordination.
In terms of the arcade game, the bag does not return after being hit, however, a score
appears on the screen of the game, which is supposed to indicate the power of the fighter
who had recently punched. These scores are not accurate measures of force as they do not
have any units of measure, though the higher the score, indicates the more force applied to
the bag.
In a real boxing fight, boxers can aim for the head or body of their opponent, meaning from
the waist line up to their head. Though the most common and basic target is the head. As
the fight progresses, the fighters proceed to endure repeated blows and strikes, some from
which they might proceed the fight, and some from which they might be knocked down. For
those that do not knock them down, every time that they are struck on the head, the head
tends to bop back and forth, or left and right, depending on which type of strike the head has
taken. The jab and cross punches, meaning from the lead and back hand going straight at
the fighters head, tend to result in the fighters head moving back and forth, whereas the
hook punches, swooping in a c shape from the fighter to his/her opponent, result in their
opponent’s head pulling to the left or right, depending on which hook was thrown (right or
left), then coming back. And as for uppercut punches, the hand comes in from below, going
upwards for the bottom of the opponent’s chin. This has the same effect as the jab and cross
punches, resulting in the head moving back then coming back to forth, like the speed
punching bag.
The types of strikes go in order of power from least to greatest go as follows:
● Jabs and Crosses (Least)
● Hooks
● Uppercuts, (more momentum swinging upwards)
Uppercut (Head Bops back, Similar to jab/cross) Result of a jab/cross (Head Bops Back)
Result of Hook (Head pulls to side)
To experiment with this, a pendulum model can be used to investigate the periodicity of the
waves being formed. Using a string and a bob pendulum model, our independent variable
could be the thickness of the string, to which we increase, corresponding to the order of
strike power. (jab, hook, uppercut).
Newton’s second law 𝐹 = 𝑚𝑎 implies that with increasing mass, even with a constant
acceleration, the force should proportionally increase. By increasing the thickness of the
string, it implies that we increase the mass of the string, therefore meaning that the thicker
the string, the more powerful the strike.
Research Question:
How does the thickness of a string supporting a bob, corresponding to a type of strike,
attached to a bench, in order to form a pendulum, affect the periodicity of the wave function
formed by the bobs movement.
Hypothesis:
If the thickness of the string is increased in accordance with the increasing power of strikes,
then the wavelength of the periodic wave will increase, meaning the frequency of the wave
has decreased.
The mass of the string will mean that the pendulum will take longer to come back to
equilibrium, reflecting a head being punched by a more powerful strike, less likely to come
back, and more time. The frequency of the waves shall decrease.
Method:
IV DV and Controlled: