The Physics of Linear Acceleration

Sir Isaac Newton (1642 – 1727) is widely recognized as one of the most influential scientists of all time.  When he was 23 years old he developed the theories of Gravitation.  Then in his 40’s he came up with his Three Laws of Motion in the “Principia Mathematica Philosophiae Naturalis”.

Here are his three Laws…

  1. “Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it”
  2. “Force is equal to the change in momentum (mV) per change in time. For a constant mass, force equals mass times acceleration.”  F = m a
  3. “For every action, there is an equal and opposite re-action”

The motion of many objects today can be explained and described through his principals from flying a plane, all the way down to what I’m going to explain today…a sprint!!!

So let’s begin…

  1. An object at rest stays at rest, an object in motion stays in motion with the same speed and in the same direction unless it is compelled to change that state by forces impressed upon it.

Let’s say you are about to start a race against someone. You get into your sprinters stance and you are waiting for go signal.  You are going to stay at rest until a force changes your state.  But, in order to move the force has to be great enough to overcome inertia.  It’s crazy that NASA actually thinks about this stuff.

  1. The acceleration of an object is dependent upon two variables, the net force acting upon the object and the mass of the object.

As an athlete’s force production increases, so will their acceleration.  What does this mean?  As you get stronger, you should get faster…it’s a Physics thing.  If an athlete is able to produce a proportionally higher force to mass ratio by gaining lean muscle mass, it will help them accelerate more rapidly.

  1. For every action, there is an equal and opposite reaction.

When an athlete strikes the ground with their foot there is a force that is produced.  The  ground says, “right back at you” then puts force back on the athlete, of which the outcome is forward movement.  Faster athletes produce more force relative to their mass than slower athletes, and therefore have greater horizontal velocity.  (Mero et al, 1992)

Now that some Physics was dropped on you, let’s keep it simple.  The ultimate goal of our Sports Performance Training at Athletes Arbor is to make sure the athletes are faster, stronger, and more explosive on their respective playing surface…and not talk about Physics to the kids.