Given, [Equation 1]
[Equation 2]where c is an arbitrary constant.
Given thatv=0 when t=0. Hence,from (2),we obtain
so that . So,(2) becomes,
Integrating (3), 
where d is a constant.
Given that r=0 when t=0. Henc efrom (4),we get
. Now,(4) becomes
On simplification,we get