Question

1) What are the two conditions where Newton’s Laws of Motion break down?

2) What are the two postulates of Special Relativity?

3) What is an inertial frame of reference?

Answer 1

Newton's laws of motion break down in following two condition

1) when velocity of body is too high i.e. of the order of speed of light them mass varies with speed so newton's Laws are not applicable

2) when reference frame is non inertial then newton's Laws are not applicable.

Q2.

Postulate of special theory of relativity are:

1) The laws of physics are the same and can be stated in their simplest form in all inertial frames of reference.

2)The speed of light in vacuum has the same value c in all inertial frames of reference and independent of relative motion of source.

Q3. Those reference frame in which Newton's Laws of motion are true are called inertial reference frame. All reference frames at the state of rest or uniform motion are inertial reference frame.