NEWTON’S 2nd LAW
m is the “inertia” of “mass”
a is the “acceleration”
The acceleration can be measured in terms of lengths and times (change in speed per unit time) such as (meters/second)/second
Force has no independent meaning outside this equation.
Masses are determined relative to each other in collisions, hence their absolute value involves an arbitrary constant.
Thus the equation F = m a
(Fc2) = (mc2 ) a
f = M a
Thus E = mc2 is like converting an absolute temperature from Fahrenheit to Celsius degrees –
all are measures of aspects of the energy of a system.