Final answer:
The net electric field midway between two equal but opposite charges is zero because their individual electric field contributions cancel each other out.
Step-by-step explanation:
The question is asking to find the magnitude of the net electric field at a point midway between two charged particles fixed on the x-axis, with one having a negative charge and the other an equal positive charge. To calculate this, we can use the principle of superposition for electric fields. Since the charges are equal and opposite, and we're finding the electric field at a point midway between them, the electric field contributions from each charge will be equal in magnitude but in opposite directions along the x-axis. Therefore, the electric fields will cancel each other out, resulting in a net electric field of zero at that point.