  Using force as a probe to map the folding landscapes of RNA molecules has
become a reality thanks to major advances in single molecule pulling
experiments. Although the unfolding pathways under tension are complicated to
predict studies in the context of proteins have shown that topology plays is
the major determinant of the unfolding landscapes. By building on this finding
we study the responses of RNA molecules to force by adapting Gaussian network
model (GNM) that represents RNAs using a bead-spring network with isotropic
interactions. Cross-correlation matrices of residue fluctuations, which are
analytically calculated using GNM even upon application of mechanical force,
show distinct allosteric communication as RNAs rupture. The model is used to
calculate the force-extension curves at full thermodynamic equilibrium, and the
corresponding unfolding pathways of four RNA molecules subject to a
quasi-statically increased force.Our study finds that the analysis using GNM
captures qualitatively the unfolding pathway of \emph{T}. ribozyme elucidated
by the optical tweezers measurement. However, the simple model is not
sufficient to capture subtle features, such as bifurcation in the unfolding
pathways or the ion effects, in the forced-unfolding of RNAs.
