A simple barometer is constructed using a liquid \(Q_{1}\) of density 16.2\(g/cm^{3}\). Calculate the least lenth of the tube to be used to measure pressure of 1.5atm. [Density of mercury = 13.6\(g/cm^{3}\), 1atm = 76.0 cm of Mercury]

  • A 1358mm
  • B 957mm
  • C 760mm
  • D 638mm
waec 2018physics

The correct answer is D. 638mm

Let \(h_{Q}\) and \(\rho_{Q}\) be the least length and the density of \(Q_{1}\) 

while \(h\) and \(\rho\) are the length and density of mercury respectively.

\(h\times \rho \times g = h_{Q} \times \rho_{Q} \times g\)

\(76cm \times 13.6 \times 10 = h_{Q} \times 16.2 \times 10\)

\(h_{Q} = \frac{76\times13.6\times10}{16.2\times10}\)

\(h_{Q} = \frac{10336}{162}\)

\(h_{Q} \approxeq 63.8cm = 638mm\)

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