A small solid sphere of mass \(m\) is released from rest at time \(t = 0\) in a deep tank filled with a viscous fluid. As the sphere falls, the fluid exerts a resistive drag force on the sphere of magnitude \(F_D = bv\), where \(b\) is a positive constant and \(v\) is the downward speed of the sphere. The buoyant force exerted by the fluid on the sphere is negligible.