Electric Field Question Involving Springs and SHM

[uazaga]

Homework Statement

A block having mass m and charge + Q is connected to a spring having constant k. The block lies on a frictionless horizontal track, and the system is immersed in a uniform electric field of magnitude E, directed as shown in Figure P25.11. If the block is released from rest when the spring is unstretched (at x = 0),
Image of problem here: http://www.solutioninn.com/images/P-M-E-P%20(11).PNG
(a) By what maximum amount does the spring expand?
(b) What is the equilibrium position of the block?
(c) Show that the block’s motion is simple harmonic, and determine its period.
(d) Repeat part (a) if the coefficient of kinetic friction between block and surface is μk.

Homework Equations

F(electric) = Eq
F(spring) = kx

The Attempt at a Solution

a) Drew a FBD and saw that Fs = Fe, so kx = Eq, therefore x = Eq/k
is that as far as i can go or can I solve this to find numbers?

b) the equilibrium position of the block would be the blocks initial position plus the change in x of the spring

c) i am really not sure how to solve this, if you could lead me in the right direction that would be nice

d) Fs + fk = Fe, so kx + μmg = Eq, therefore x = (Eq - μmg) / k

 

[uazaga]

does anyone have any idea on how to solve this electric force problem that involves a spring?