show tha the rate of change of momentum = mass * accelaration.Under what condition does this relation hold?

Consider a body of mass m having an initial velocity u,Then initial momentum of this body=mu

(Since momentum=mass x velocity)

Suppose after time t its final velocity becomes v

then final momentum=mv

Now change in momentum=final momentum-initial momentum

 =mv-mu=m(v-u)

Rate of change in momentum=m(v-u) / t

=m x a(since rate of change in velocity is defined as the acceleration i.e. a=(v-u) / t
The relation is valid for uniformly accelerated motion.
Regards