$($Question $2)$

$($a$)$ Calculate the celerity of pressure in open fresh water at $20C.$

$($b$)$ what will the celerity be if the water is contained in a cast$-$iron pipe with $489mm-$ inside diameter and $14\mathrm{.}3-mm$ wall thickness?

$($c$)$ express the celerity in the pipe as a percentage of the celerity in the open air. Knowing that, $$ water at $20C=988\mathrm{.}2k\frac{g}{m^3},$ bulk modulus of elasticity of the water $=2\mathrm{.}07{10}^{6}K\frac{N}{m^2},$ modulus of elasticity of the cast$-$iron $=103{10}^{6}K\frac{N}{m^2}.$

$(5$ Marks$)$