Problem $1$

A lead ball, $0\mathrm{.}2$ inches in diameter, is quenched in $90F$ oil from

an initial temperature of $400F.$ The quenching process occurs by

dropping the ball into the oil. It takes $15s$ to fall from the oil surface

to the bottom of the quenching bath. The convective heat$-$transfer

coefficient between the lead and oil is $40Bt\frac{u}{h}f{t}^{2}F.$

what is the Bi number for this situation?

what will be the temperature of the ball as it hits the bottom of the

bath?