Block A of mass \(m_A\) rests on a horizontal, frictionless track. A lightweight string is attached to the left side of Block A, runs horizontally to the left, and is wrapped around a solid, disk-shaped pulley. The pulley has rotational inertia \(I\) and radius \(R\) and is free to rotate on a fixed, frictionless horizontal axle. Block B of mass \(m_B\) is stationary on the track a distance \(D\) to the right of Block A.

A small fan mounted on top of Block A is turned on and exerts a constant rightward force of magnitude \(F_0\) on the block. The system is released from rest, and Block A accelerates to the right, causing the string to unwind from the pulley without slipping.

Exactly as Block A travels the distance \(D\) and reaches Block B, the string fully unwinds and detaches from the pulley. Block A then collides completely inelastically with Block B. The mass of the fan is included in \(m_A\).