Question: How can i find the coeffients of My parameter in the following physics expression

Hey dear friends, in the following code (which is also attached at bottom of this post)

restart;
with(Physics[Vectors]);
Setup(mathematicalnotation = true);
with(Physics);
Setup(op = {H, I__C, I__G, Omega, R, a_, p, r, rho, v_, `α_`, `ω_`, `ϰ_`})
Newton_generalized_MatForm := m*(Omega*rho*H(t)*diff(`ϰ_`(t), t) - rho*diff(H(t), t)*diff(`ϰ_`(t), t) - rho*H(t)*diff(`ϰ_`(t), t, t) + diff(v_(t), t)) = f_[c] + f_[g]

 i wish to get the  (kappa-dot) coefficients 

so I used the "Coefficients" function as follows:

Coefficients(Newton_generalized_MatForm, diff(varkappa_(t), t))

but the results aren't as expected and it's this:

so is there a way around this , thanks in advance
Coeff.mw