Question

Some examples and limitations of Newton's laws

Answer 1

Limitations on Newton's 2nd Law

One of the best known relationships in physics is Newton's 2nd Law



but, though extremely useful, it is not a fundamental principle like the conservation laws. F must be the net external force, and even then a more fundamental relationship is



The net force should be defined as the rate of change of momentum; this becomes



only if the mass is constant. Since the mass changes as the speed approaches the speed of light, F=ma is seen to be strictly a non-relativistic relationship which applies to the acceleration of constant mass objects. Despite these limitations, it is extremely useful for the prediction of motion under these constraints.

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Limitations on Newton's 2nd Law

One of the best known relationships in physics is Newton's 2nd Law



but, though extremely useful, it is not a fundamental principle like the conservation laws. F must be the net external force, and even then a more fundamental relationship is



The net force should be defined as the rate of change of momentum; this becomes

only if the mass is constant. Since the mass changes as the speed approaches the speed of light, F=ma is seen to be strictly a non-relativistic relationship which applies to the acceleration of constant mass objects. Despite these limitations, it is extremely useful for the prediction of motion under these constraints.