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Question 30187
JEE Physics · Hard

Errors and Measurements: Error — Subtraction Danger MCQ

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Error — Subtraction DangerHardQuestion 30187

Question

Why is subtraction of two nearly equal measured quantities considered unreliable?
  1. A
    The absolute error stays fixed, but relative error becomes very large
    Correct
  2. B
    The absolute error increases on subtraction
  3. C
    No reason — it is always reliable
  4. D
    Sig figs increase on subtraction

Correct answer

The absolute error stays fixed, but relative error becomes very large

Explanation

If A ≈ B, then A − B ≈ 0, making the relative error (ΔA+ΔB)/(A−B) enormous even if absolute errors are small.

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