γ = 1.4;  (Subscript[c, p]) = 1004; 
    R = (γ - 1)/γ* (Subscript[c, p]); Tt4 = 1400; 
    T0 = 216;

fa0[T0_] := (Sqrt[γ R T0])

fτr[M0_] := 1 + ((γ - 1)/2) (M0^2)

Clear[Tt4, T0]
fτλ[Tt4_, T0_] = Tt4/T0

fτλ[Tt4, 5. ]

fτr[M0]

fFBm0[T0_, Tt4_, M0_] = 
      fa0[T0]*(M0*Sqrt[fτλ[Tt4, T0]/fτr[M0]] - 
            M0)

Plot[fFBm0[216. , 1900. , M0], {M0, 0, 7. }, 
        AxesLabel -> {(Subscript[M, 0]), (F/(Subscript[m, 0]))}];

Plot[
        Evaluate[Table[fFBm0[216. , Tt4, M0], {Tt4, 1600, 2200, 300}]], {M0, 
          0, 7. }, AxesLabel -> {(Subscript[M, 0]), (F/(Subscript[m, 0]))}];