Homework Help: Time Period of SHM

1. Oct 13, 2011

Asphyx820

1. The problem statement, all variables and given/known data

Two Springs are present (one just infront of the other). The Spring towards the left has +Q charge and towards the right -Q charge (at their ends).The distance between the two charges is d. The Springs are of length l. Find the Time Period of the Simple Harmonic Motion if the charges are of same mass. ( l > d )

Diagram
(Wall)-->(Spring)-->+Q -Q<--(Spring)<--(Wall)

2. Relevant equations

F(elec)=(k Q^2) / (d^2) where k=(1/4)∏ε
F(Spring)=( Kl )

3. The attempt at a solution

I know the above two equations, but cant proceed. Is there any other force too? I cant figure out why will the charges move back again? I'm having two confusions

1) The charges are opposite so they will attract each other. When they reach a certain point they will collide (as l > d ) and move back. Is this the reason why they move back? What other equation do i have to use?

2) Is it the Spring force will pulls the charges back before they collide. But it shouldn't be true as ( l > d ) and electrostatic forces are very strong and spring force cannot overcome it. Am i right? so how should i proceed

Pls help me....

Last edited: Oct 13, 2011
2. Oct 13, 2011

danielakkerma

Hello there,
It would be of tremendous use, if you could provide us with a diagram of how the setup looks like, as it is rather unclear from the initial description.
Meaning,
Are the charges connected like so:
Q->spring->spring-(-)Q?
With the total distance d?
Or,
Fixture->Spring->Q-Spring-(-Q)->Fixture.
Are there any other limitations, constraints?
Beware that after you provide the full delineation of the problem, there might arise a need to solve a differential equation, so that you incorporate, simultaneously, the electric and elastic force.
Daniel