The Field Goal
Kickers in the NFL and NCAA
are notoriously hated when they miss a
field goal, but it turns out field goals
are not as simple as they seem.
A field goal is one of the
many examples of projectile motion in
sports. Projectile motion, is when an
object is traveling through the air
with an initial velocity and is being
acted upon only by gravity. In a real
football game, there are other forces
acting on the ball in the air, namely
air resistance. However the
calculations with air resistance are
beyond the scope of this page and the
assumption that there is no air
resistance gives an accurate estimate
of the football's motion.
Momentum
Momentum is how
the kicker will give a bigger
force to the ball when it is
kicked. The law of
conservation of momentum
states that momentum before
always equals momentum after.
That means, in the system of
the ball and the kicker, the
momentum of the two objects
before will equal the momentum
after. Momentum is described
as mass times velocity. This
means that if the kicker has a
higher velocity when he kicks
the ball, the ball will have a
higher velocity and therefore
travel farther. This is why
kickers find it essential to
get a running start at their
kicks
Projectile Motion
The
equations for
projectile motion can
be found under the
basketball section of
the page, and the
calculations are
exactly the same. Once
the ball is kicked, it
is no longer affected
by any other force
besides gravity (under
the assumption that
air resistance is
negligible). Therefore
by simply knowing the
initial velocity of
the football, which is
found by using
momentum you can tell
how fast the ball must
be kicked to reach the
goal posts.