Exam-style question
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A student measures the length of a metal rod as 50.0 cm with a possible uncertainty of ±0.5 cm. What is the combined absolute uncertainty if the student measures the length of two rods?.
- A.±0.5 cm
- B.±1.0 cm
- C.±0.25 cm
- D.±2.0 cm
Model answer
What a good answer should say
- ±1.0 cm
Explanation
Why this works
When measuring two rods, the absolute uncertainties add up. The formula for combined absolute uncertainty is: U_total = U1 + U2.
Substituting gives U_total = ±0.5 cm + ±0.5 cm = ±1.0 cm. Thus, the combined absolute uncertainty is ±1.0 cm.
Common mistake
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