Cartoon showing time series of slingshot “ejection” of a protostar from the ISF. Left to right: (1) core forms in filament; (2) core evolves into protostar and remains mechanically entrained in accelerating filament; (3) protostar continues to gain mass but remains in filament due to relatively low instantaneous filament acceleration; (4) filament reaches maximum acceleration (toward left) so that inertia of protostar causes it to leave filament, decoupling from dense gas cradle; (5) “ejected” young star moves away from filament.