A particle of mass $m$ is projected with velocity $v$ making an angel of $45^{\circ}$ with the horizontal. When the particle lands on the level ground the magnitude of the change in its momentum will be :

Question

$\begin {array} {1 1} (1)\;Zero & \quad (2)\;2\: mv \\ (3)\;mv\: /\: \sqrt2 & \quad (4)\;mv\: \sqrt 2 \end {array}$