Physics of Archery
Kinematics and Achery
As is the case with any launched projectile, an arrow too follows a set motion specific to its physical design, its aimed course and its velocity and acceleration upon release. It is these factors that directly relate back to the aspect of physics known as kinematics.
Firstly, any archer initially firing an arrow performs what is known as the cast,
which is defined as the arrows speed and distance. The effectiveness of the cast is
greatly influenced by the arrow itself. The arrow is compiled of a nock (the end that fits
into the bow string) the fletchings , the lightweight shaft and the arrow head. The
purpose of the fletchings is to increase the drag of an arrow, thus stabilizing it during
flight. In order for this to be made possible, the center of drag, (the point where the
concentration of drag resides) must be located behind the center of mass. As a result,
the arrow’s head is made heavier in proportion to its other parts to increase the distance
between the centers of drag and mass; the further they are from each other, the the more
stable the arrow will be in flight.
When an arrow is fired, it reaches its maximum velocity shortly after its initial release from the bow. This velocity is influenced by the drawback of the bow- or the strength placed in the shot. However, what greatly influences an archer’s ability to hit their mark is acceleration. Acceleration describes the change in velocity over a certain span of time. Firstly, although the fletchings of an arrow provide mid-air stability, they also create a drag factor. Drag is the force that opposes an object moving through a fluid (air). With this increase in drag, there will inevitably be a decrease in velocity, or deceleration. As a result, once fired, an arrow will very slowly begin to lose speed.
In addition, an arrow follows an arc, or a parabolic flight path. Subsequently, an arrow is classified as a projectile and, thus, has no horizontal acceleration. This means that (if air resistance is negligible) the horizontal velocity of the projectile remains constant until it reaches the intended target. However, the vertical velocity is continuously changing. Once fired, the vertical velocity of the arrow gradually begins to decrease as a result of gravity. At the “vertex” of its parabolic flight, the vertical velocity has a magnitude of zero. Then, the vertical velocity of the arrow increases ( to the initial velocity) in the downward direction, indicating an increase in acceleration due to gravity. The arrow will continue to accelerate downward until it reaches the target.
-Components of a typical arrow.
-Graph which demonstrates the relationship between vertical velocity and time.
-Parabolic flight path of the arrow