CAUSE AND EFFECT

[James Espinosa <F_ESPINOSA@TWU.EDU>]

I certainly agree with Leigh and others who state that Newton's Second Law expresses a net force as the cause of the acceleration of a body.  John disagrees and brings up the symmetry property of an equation.  I would like to make a few points:

 

1.  Newton did not use algebra in stating his Second Law of Motion, and it is clear from how he expressed it that he intended for force to be what produced a change in motion.

2.  Cause and effect is not a mathematical property; it is a physical, theoretical characteristic.  The sign "=" is indeed a logical constant that in mathematics has the property of symmetry, and also of being reflexive and transitive thereby defining equivalence classes.  But, in the Second Law I would say that "=" only means that the numerical value on one side is identical with the numerical value on the other side.

3.  There is an asymmetry in the Second Law.  When the Law is used, the force is produced by the environment but the acceleration is that of the body.  So, the cause is from the environment while the effect is on a property of the body, its acceleration.

4.  In mechanics the cause and the effect are at the same time. 

 

James M. Espinosa