How does Newton's second law include the first law?

states that in the absence of a net force, an object will not accelerate. The second law gives the definition of that net force in the famous equation:

##F = m * a##,

where ##F## is the net force, ##m## is the mass of the object, and ##a## is the .

In the first law, the net force is zero. Since mass is not zero for any object, this makes the acceleration zero, which matches the first law:

##0 = m * 0##

So the first law is really just a special case of the second law, the case where ##F## and ##a## are zero.