Naturally occurring boron is 80.20% boron -11 (atomic mass = 11.01 amu) and 19.80% of some other
isotopic form of boron. what must the atomic mass of this second isotope be in order to account for
the 10.81 amu average atomic mass of boron?

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.