Charge q$,2$q and $$q are fixed on the vertices of an equilateral triangle of side length d$.$ The charges are

then moved closer together so that they form an equilateral triangle whose side length is now $0\mathrm{.}75$d$.$

Take q to be $4\mathrm{.}8$ nC and d to be $2\mathrm{.}3$ mm$.$

a$)$ What is ratio of the original force on

$$q$$ to the final force on $$q$$

b$)$ Determine the work required to move

the charges to the new configuration.

c$)$ Determine the change in potential due

to move at the centre of the triangle.