Question

Why can we not use the length of a rod as a standard unit?

• A. Its length changes with temperature
• B. It corrodes with time
• C. It is not easily reproducible
• D. It is not readily available

Answer 1

Answer: (A), (B), (C)

It is not easily reproducible

A rod expands when the temperature increases and contracts when it decreases. Also, it corrodes with time, which can affect its length. Adding to that, the length of the rod cannot be exactly matched when it is being replicated. These factors lead to the fact that the length of the rod cannot be considered as a standard unit, because the standard unit should not vary with time and place.