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JAMB Physics 1988 Question 15

Question 15

Pressure

When one arm of a U-tube manometer is connected to a gas supply, the levels of mercury in the two arms of the U-tube are as shown in the diagram above. If the atmospheric pressure is 76.0 cm Hg, the gas pressure is

Diagram for this question
  1. A.62.6 cm Hg
  2. B.72.5 cm Hg
  3. C.79.5 cm Hg
  4. D.85.9 cm Hg
Show the answer and explanation

Answer: D (85.9 cm Hg)

Explanation

The mercury in the open arm stands 13.4 − 3.5 = 9.9 cm higher, so the gas pressure is 76.0 + 9.9 = 85.9 cm Hg.