"Harshal" wrote in message
...
The question is -
Why comets have parabolic or hyperbolic path instead of having
ellipticalpath as other planets?

Repeating comets do have elliptical orbits. It's
the one-time-only comets which have too much energy
to remain gravitationally bound to the Sun that have
parabolic or hyperbolic trajectories.

Comet Halley, for example, has an elliptical orbit
(ignoring perturbations it picks up from the other
solar system bodies on each pass).