Question

Which one of the following statements concerning proper length of a meter stick is true? Explain

1. The proper length is always one meter
2. The proper length depends upon the speed of the observer
3. The proper length depends upon the acceleration of the observer
4. The proper length depends upon the reference frame in which it is measured
5. The proper length is the length measured by an observer who is moving with respect to the meter stick.

Answer 1

This phenomenon is related to the Special theory of relativity.

option D is correct . The proper length depends upon the reference frame in which it is measured.

option A not true because nothing is absolute , everything is relative so with respect to the reference frame length changes

Option B not true because the observer must be at rest with respect to the meter stick so not dependent on the length and it should not also accelerate so option C is not true also.

option E wrong because there is length contraction when observer is moving with respect to the meter stick.