[" In a free space,a rifle of mass "M" shoots a bullet of "],[" mass "m" at a stationary block of mass "M" distance "],[" D away from it.When the bullet has moved through "],[" a distance d towards the bullet has moved through "],[" of the bullet-block system is at a distance of mass "],[" of the bullet-block system is at a distance of mass "],[" (1) "(md+MD)/(M+m)" from the bullet "],[" (2) "(md+MD)/(M+m)" from the block "],[" (3) "(2md+MD)/(M+m)" from the block "],[" (3) "(2md+MD)/(M+m)" from the block "],[" (3) "((D-d)M)/(M+m)" from the bullet "],[M+m]