Direction: A particle initially (i.e., at time \[t=0\]) moving with a velocity u subjected to a retarding force, as a result of which it decelerates at a rate \[a=-k\,\sqrt{v}\] where v is the instantaneous velocity and k is a positive constant.The particle comes to rest in a time

• A. \[\frac{2\sqrt{u}}{k}\]
• B. \[\frac{\sqrt{u}}{k}\]
• C. \[2k\sqrt{u}\]
• D. \[k\sqrt{u}\]