From Newton's second law, F=dp/dt = d(mv)/dt =
m×dv/dt + v×dm/dt
if Mass remains constant and is independent of time, only then we can say that dm/dt = 0 and the equation reduces to F= m×dv/dt = ma
But if Mass is somehow dependent on time, then The eqn F= ma does not hold good.

Explanation:

The relation F=ma, also known as Newton's second law of motion, states that the force acting on an object is directly proportional to its mass and acceleration. This equation is fundamental in understanding the relationship between force, mass, and acceleration in classical mechanics. However, there are certain scenarios in which the relation F=ma cannot be deduced from Newton's second law, and one such scenario is when the mass depends on time.

Mass depends on time:
If the mass of an object changes over time, then the relation F=ma cannot be directly applied. This is because the equation assumes a constant mass throughout the motion. If the mass is not constant, the equation becomes inaccurate and cannot be used to determine the force exerted on the object accurately.

Example:
Let's consider an example to illustrate this point. Imagine a rocket launching into space. Initially, the rocket has a certain mass, and it experiences a force due to the expulsion of gases from its engines. However, as the rocket burns fuel, its mass decreases. Consequently, the force acting on the rocket changes because the mass is changing. In this case, the relation F=ma cannot be used directly since the mass is not constant.

Alternative approach:
To deal with situations where the mass depends on time, an alternative approach must be used. Instead of using Newton's second law directly, we can rely on the concept of instantaneous force and instantaneous acceleration. By considering infinitesimally small time intervals, we can determine the force acting on the object at each instant and the corresponding acceleration. Then, by integrating these values over time, we can find the overall change in momentum and relate it to the integrated force.

Conclusion:
In conclusion, the relation F=ma cannot be deduced from Newton's second law if the mass of the object is not constant and depends on time. In such cases, an alternative approach considering instantaneous forces and accelerations must be used to accurately determine the motion of the object.