Kinesiology, the scientific study of human motion, involves, in part, the application of the principles of physics to body movements. There are some basic ideas in kinesiology which are pertinent to skating. These have the potential to greatly improve one's skating ability, allow one to experience profound ideas at play in the real world, and overall inject depth into the skateboarding experience. I believe that such knowledge is another rule of thumb for success and it has certainly been a part of my journey in the craft. Do not be discouraged from reading the following few posts if you are unfamiliar with physics or maths because the principles are explained in very simple terms with minimal technical jargon.
Let's begin by exploring the fundamentals of physics.
1. Isaac Newton's 3 laws of motion:
a) Inertia: An object will not move or stop moving unless acted upon by an external force.
b) Force: The force that an object exerts is equivalent to its acceleration times its mass.
c) Reaction: Every action has an equal and opposite reaction.
Let's first grasp these laws in general terms and then apply them to skating.
a) The ball that never stops rolling:
It's quite obvious that a ball will never start rolling on a level surface unless pushed. It's less obvious that it will never stop rolling unless obstructed. This is because commonsense has us believe that it would stop rolling when the force which pushes it has been exhausted. According to Newton, however, if a ball slows down and stops it is only because some other force - wind, gravity, rough surface, or some other form of resistance - brought it to a halt, otherwise, it would continue rolling forever. The idea that objects will remain in a particular state of motion unless acted upon by an external force is termed inertia.
b) The weak brick:
If a bullet is so small why is it so powerful? The bullet accelerates so quickly when shot from a gun that its speed makes it exceptionally forceful. Conversely, a brick thrown at a person's back with little acceleration will bear relatively little force and cause no more damage than a graze. Thus it's speed and mass in conjunction that reveals the magnitude of the force that an object exerts.
c) The pushy couch:
When you push a couch, the couch pushes you back with the same force that you apply to it. This is why we sometimes strain our muscles when pushing couches - yes, the couch pushed us back! Sometimes we want to be pushed in this way and sometimes we don't. When we jump, it's the ground that thrusts us up; when we fall, it's the ground's push that injures us.