In this question use $g=9.8$ m s${}^{-2}$

A particle $P$ of mass 2m kg lies on a smooth horizontal table.

$P$ is attached to one end of a light inextensible string. The string passes over a smooth pulley fixed at the edge of the table, and a particle $Q$ of mass $m$ kg hangs freely at the other end of the string.

The string between $P$ and the pulley is horizontal, and the string between the pulley and $Q$ is vertical.

A constant horizontal force of magnitude 19 N acts on $P$ away from the pulley.

The system is released from rest with the string taut, as shown in the diagram below.

The system moves with acceleration 2 m s${}^{-2}$, with $Q$ moving downwards.