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Question
The masses of two bodies are measured to be 15.7 ± 0.2 kg and 27.3 ± 0.3 kg. What is the total mass of the two and the error in it?
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Solution
Given: A ± ΔA = 15.7 ± 0.2 kg and
B ± ΔB = 27.3 ± 0.3 kg.
To find: Total mass (Z), and total error (ΔZ).
Formulae:
i. Z = A + B
ii. ± ΔZ = ± ΔA ± ΔB
Calculation: From formula (i),
Z = 15.7 + 27.3 = 43 kg
From formula (ii),
± ΔZ = (± 0.2) + (± 0.3)
= ± (0.2 + 0.3)
= ± 0.5 kg
Total mass is 43 kg and total error is ± 0.5 kg.
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