Physics of Field Hockey

Have you ever heard of “Energy, Force, Friction, Momentum, Motion and Newton’s Laws”? Is it possible to relate these science terms to a day-to-day activity like a sport? The answer is YES! Field hockey is a great example of Physics in Action. Once, I was a forward field hockey player, and I kept practicing with dribbling and shooting the ball. Only after starting to follow Physics that I understood, how much of my favorite sport was governed by it.
An important fact in Field hockey is that, players prefer playing on artificial turf grounds to natural grounds, even though the latter is more abundant in the country. Generally, it is easy to maintain the speed of the game on an artificial turf. This is due to a force known as “Friction”. Friction is the resistance to the motion of two moving objects or surfaces that are in contact. The grass fields have uneven long grass, while the turf has shorter and smoother synthetic grass blades. This makes its coefficient of friction to drop. In other words, by applying the same force on both fields, the ball will move faster and further on turf. Also, the even surface of the turf will not slow down the momentum of the moving ball, as much as a bumpy natural surface would do. If you have ever wondered why water is sprayed on turfs before the start of a match (and during the half break), it is also for the same reason. Water acts as a lubricant on the field, and it achieves the same desired effect of reducing the friction between ball and ground.
The game of field hockey follows a set of Fundamental Laws in Physics, known as “Newton’s Laws of Motion”. Sir Isaac Newton published these three laws in 1687, and they can be applied to all objects at rest or at move (in air or on grounds) that we come across in our day-to-day lives.
According to Newton’s first Law of Motion (also known as “Law of Inertia”), an object at rest would stay put, and an object in motion would keep moving with a constant speed (without changing the direction), unless it is acted upon by an external force. This is the reason for the ball to follow a straight line when hit, until it is disturbed by another player. If the ground is perfectly frictionless, then it should continue moving forever (unless disturbed).
According to Newton’s second Law, if an object is subjected to an external force, then the net force acting on it is equal to the product of mass of the object and the object’s acceleration (change of speed). Simply put,

When two different forces are applied to the ball (say one is hitting the ball, while the other is tapping it), according to the second law of motion, the ball that is being hit will move with a higher speed than the ball that is being tapping.
Newton’s third Law of Motion states that for every action, there is an equal and opposite reaction. Due to this reason, whenever a hit is made, an opposite force is applied on the stick. To absorb this force better, hockey sticks are now made in carbon fibers, which are far better in absorbing shocks than earlier wooden sticks.
Also, all of the shooting techniques in hockey obey basic Physics principals. Consider the simple action of “Hitting” the ball. Here, the field hockey player begins the shot by raising his/her hockey stick behind her body as shown below.
There is a potential energy stored on the stick and when the stick comes closer slightly behind the hockey ball; according to the conservation of energy, the total stored energy turns into a kinetic energy. Next, the stick touches the ball that is at rest, will start to move in the same direction of the moving stick obeying the conservation of momentum. That is, for a collision occurs between objects in an isolated system, the total momentum before the collision is equal to the total momentum after the collision. Therefore, the powerfulness of the two shots namely ‘hit’ and ‘push’ are, pushing the ball is mainly depend on the players’ strength while the hitting depends on the stored energy of the hockey stick. No wonder why small sized players hit the ball faster. Next time, you play or watch a game, think about all the forces and accelerations at work. It is truly impressive to realize that you can understand the Physics Laws that are in action during your favorite sport. There is no magic behind anything, only the Laws of Physics in everywhere.

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  1. This article was sent in by Sathsala Oshadhi Gamage. She is a Science postgraduate degree holder from University of Peradeniya. You can contact her on Facebook