Clarification in the definition of force

[manimaran1605]

\According to Newton's second law, force is defined as rate of change of momentum or force is defined as product of mass into acceleration, I both of these definitions are same and right.

My questions are,
(1) how can i prove this two definitions are same?

 

[zhangwfjh]

F=dp/dt=d(mv)/dt=m(dv/dt)=ma
Actually, these two definitions are not equivalent in the framework of special relativity.