$(5)$ A copper pin fin $0\mathrm{.}25$ cm in diameter that protrudes from a wall at $95C$ into ambient air at $25C.$ The heat

transfer is mainly by natural convection with a coefficient equal to $10\frac{W}{m^2}-K.$ Calculate the heat loss,

assuming that:

$($a$)$ the fin is infinitely long, $($b$)$ the fin is $2\mathrm{.}5$ cm long, and $($c$)$ how long would the fin to be for the

Infinitely long solution to be correct within $5\%?$

$[$Ans: $($a$)0\mathrm{.}865$ W $,($b$)0\mathrm{.}140$ W $,($c$)L>28\mathrm{.}3cm]$