Given :
Pressure, P = 0.4 lb/in².
Depth, h = 42 in.
To Find :
The density of a liquid.
Solution :
Pressure at height h of a liquid of density [tex]\rho[/tex] is given by :
[tex]P = \rho g h[/tex] ....1)
Here, g = 386.04 in/s²( acceleration due to gravity )
Putting all values in equation 1, we get :
[tex]P = \rho g h\\\\0.4 = \rho\times 386.04 \times 42\\\\\rho=\dfrac{0.4}{42\times 386.04}\ lb/in^3\\\\\rho=\dfrac{0.4}{42\times 386.04}\times 12^3\ lb/ft^3\\\\\rho=0.0426\ lb/ft^3[/tex]
Hence, this is the required solution.