State Newton’s second law of motion. Under what condition does it take the form F = ma ?

Newton’s second law of motion states that —

The rate of change of momentum of a body is directly proportional to the force applied on it and the change in momentum takes place in the direction in which the force is applied.

The mathematical form of Newton’s second law of motion is —

F = ma

where,

F = force
m = mass and
a = acceleration

The conditions for the relation to hold true are —

1. velocities must be much smaller than the velocity of light.
2. Mass of the body should remain constant.