How can second equation of motion is reduced to first equation of motion?

Answer 1

let a Body moving with initial velocity 'u' changes its velocity to 'v' in time 't'

then ,

acceleration 'a' = (v-u)/t

=> a * t = v - u

=> a * t + u = v

=> v = u + a * t

Answer 2

We'll take a crack at it:

Newton's second law of motion says that [ F = m A ].

(Force = mass times acceleration)

If you take that statement and make the force zero, you have [ m A = 0 ].

Since the mass doesn't change, this tells you that the acceleration is zero.

From that, you can confidently announce:

"A body with no external forces acting on it experiences no acceleration,

which means that its speed or direction don't change, which means that it

remains in constant, uniform motion."

And that's exactly the statement of Newton's first law of motion.

So we have, prima facie and pro bono, "QED et Reductio ad Absurdum".