Two putty balls of equal mass moving with equal velocity in mutually perpendicular directions, stick together after collision. If the balls were initially moving with a velocity of \[45\sqrt{2}\,m{{s}^{-1}}\] each, the velocity of their combined mass after collision is [Haryana CEE 1996; BVP 2003]

• A.             \[45\sqrt{2}\,m{{s}^{-1}}\]
• B.               \[45\,m{{s}^{-1}}\]
• C.             \[90\,m{{s}^{-1}}\]
• D.               \[22.5\sqrt{2}\,m{{s}^{-1}}\]