Armature: $i_a=\frac{e_a-v_b}{R_a},e_{\text{n}\text{e}\text{t}}=e_a-v_b$

Compute $\frac{I_a(s)}{E_{\text{n}\text{e}\text{t}}(s)}$

Mechanical load: $J_e{}_m^{}={}_m-B_e{}_m,{}_L=(\frac{N_1}{N_2}){}_m$

Note: ${}_m(s)=L\{{}_m(t)\}$

Compute $\frac{{}_m(s)}{T_m(s)}$ and $\frac{{}_L(s)}{{}_m(s)}$