  Black hole thermodynamics is the area of study that seeks to reconcile the
laws of thermodynamics with the existence of black hole event horizons. Here we
calculate the entropy corresponding to the interior of a Schwarzschild black
hole for massless modes, assuming the mass of the black hole increasing with
time. We find that the entropy is proportional to the Bekenstein-Hawking
expression. Also, we can see that the evaluated entropy satisfies the second
law of thermodynamics. Using the thermodynamic law we get a relation between
temperature and inverse temperature. The special relativistic corrections to
thermodynamic quantities are considered. The change in thermodynamic properties
are analyzed when the velocity of the considered system is comparable to the
speed of light. The effect of presence of scalar charge is incorporated.
