A $5m$ high retaining wall with smooth vertical back supports a dry cohesionless soil that weights $18k\frac{N}{m^3}.$

The backfill rises from the crest of the wall at an angle of $20$ with the horizontal. If the angle of internal friction

of backfill material is $30,$ determine the magnitude and point of application of active earth pressure per meter

length of wall. $[$Ans: $93\mathrm{.}15K\frac{N}{m^2},1\mathrm{.}67m]$