Exercise $3$ below.

Consider the disk sander shown in figure

The force that should be applied to the wood block is $10$ N and the coefficient of friction between disk and wood is assumed to be $2.$

Draw the stress elements at points $1$ and $2,$ show the stresses acting on them and calculate the principal stresses.

Solution : The element at point $1$ is subjected to torque due to friction force, axial force, and bending force simultaneously. Each load will create their respective stresses as shown below.C