Please explain step by step with FBD$,$ I$\text{'}$m very confused on how to do this

Find the equations of motion for the following systems. $($note: friction is assumed to be a

viscous friction with viscous damping coefficients of Bn at the contact surfaces. f$($t$)$ and

T$($t$)$ are the applied forces and torques to the mechanical systems, respectively.$)$

$($d$)$