Final answer:
The missing force that would create a net force of 0 N, when currently there is a net force of 200 N downwards, is 200 N acting upwards.
Step-by-step explanation:
The question asks for the missing force in a scenario where the net force (Fnet) is given as 200 N downwards. When calculating Fnet in a vertical direction, all the forces acting upwards and downwards need to be considered. If we have an existing Fnet of 200 N downwards, and we're looking for the magnitude of an additional force that would have resulted in a zero net force situation (meaning no net force acting on the system), we can infer that an equal and opposite force must be acting in the upward direction to balance out the downward force. Therefore, the missing force is 200 N upwards.