  Our study attempts to understand the collision characteristics of two coronal
mass ejections (CMEs) launched successively from the Sun on 2013 October 25.
The estimated kinematics, from three-dimensional (3D) reconstruction techniques
applied to observations of CMEs by SECCHI/Coronagraphic (COR) and Heliospheric
Imagers (HIs), reveal their collision around 37 $R_\sun$ from the Sun. In the
analysis, we take into account the propagation and expansion speeds, impact
direction, angular size as well as the masses of the CMEs. These parameters are
derived from imaging observations, but may suffer from large uncertainties.
Therefore, by adopting head-on as well as oblique collision scenarios, we have
quantified the range of uncertainties involved in the calculation of the
coefficient of restitution for expanding magnetized plasmoids. Our study shows
that the comparatively large expansion speed of the following CME than that of
the preceding CME, results in a higher probability of super-elastic collision.
We also infer that a relative approaching speed of the CMEs lower than the sum
of their expansion speeds increases the chance of super-elastic collision. The
analysis under a reasonable errors in observed parameters of the CME, reveals
the larger probability of occurrence of an inelastic collision for the selected
CMEs. We suggest that the collision nature of two CMEs should be discussed in
3D, and the calculated value of the coefficient of restitution may suffer from
a large uncertainty.
