Final answer:
The expression Σfi represents the electric field at a given point in space due to multiple source charges. To calculate the electric field, you need to know the positions of the charges and the location where you want to determine the field. The electric field of a circular thin disk can be calculated using a specific formula. When calculating the resultant displacement of a ball, you can find the sum of the separate displacements.
Step-by-step explanation:
The expression Σfi represents the electric field at a given point in space due to multiple source charges. It is the sum of the individual electric fields generated by each charge. To calculate the electric field, you need to know the positions of the charges and the location where you want to determine the field.
To find the electric field of a circular thin disk with a uniform charge density, you can use the formula for electric field due to a disk. This formula takes into account the radius of the disk, the distance from the center of the disk to the point where you want to calculate the field, and the charge density of the disk.
When calculating the resultant displacement of a ball, you can find the sum of the separate displacements. The magnitude of the resultant displacement can be obtained using the Pythagorean theorem, which states that the square of the magnitude is equal to the sum of the squares of the components in each dimension.