Find the force acting on Q at time t (0 < t < T).

A block P of mass M is on a smooth horizontal plane, and an object Q of mass m is always on top of the block P. Initially both P and Q are at rest. At a time t = 0, an initial speed v0 is given to P in the rightward direction. Then Q also starts to move. When a time T is passed after P is given an initial speed, the velocity of P coincides with the velocity of Q. A coefficient of kinetic friction between P and Q is denoted as µ. Treat the rightward direction as positive, and the acceleration of gravity is denoted as g.

Find the force acting on Q at time t (0 < t < T).