In case C two positive point charges 2Q are each a distance

In case C, two positive point charges +2Q are each a distance s away from a third positive point charge +q. In case D, four positive point charges +Q are each a distance s away from a fifth positive point charge +q. (The angle a shown is the same in both cases.) Is the net electric force on the +q charge in case C greater than, less than, or equal to the net electric force on the +q charge in case D? Explain

Solution

less than case D

both case C & case D are symmetrical about x-axis. In each case, all y components cancel each other and

all xcomponents add each other

but magnitude of x-component in case D is more than in case C