# Homework Help: Magnitude of initial acceleration

1. Jan 27, 2008

### sonastylol

[SOLVED] Magnitude of initial acceleration

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

A particle of mass 67 g and charge 25 microC is released from rest when it is 89 cm from a second particle of charge -10 microC. Determine the magnitude of the initial acceleration of the 67 g particle. Answer in units of (m/s)^2.

I understand how to find magnitude of vectors but I don't even know where to start with this one..

Can someone please give me a detailed push in the right direction? Thank you so much

2. Jan 27, 2008

### hotcommodity

You know Coulomb's Law:

$$F_E = \frac{k*q*q'}{r^2}$$

And you know Newton's 2nd Law:

$$F_{NET} = ma$$

If the electric force is the net force, what is the relation between these two equations?

3. Jan 27, 2008

### sonastylol

to be honest im not sure what the answer to:

If the electric force is the net force, what is the relation between these two equations?

we only just barely learned those equations, and i havent seen any type of sample problem close to this one...

I dont know where to start, even with your help..

Thanks again

4. Jan 27, 2008

### hotcommodity

The only force acting on the 25microC charge is the electric force FE, and thus the electric force IS the net force on the charge in question. So we have:

$$\frac{k*q*q'}{r^2} = ma$$

You know the magnitude and signs of each charge, you know the value of the constant "k," you know the distance between the two charges "r," and you know the mass of the charge in question. Now all you have to do is solve the above equation for the acceleration "a." Don't forget to convert the charges to Coulombs, the mass to kilograms, and the distance to meters. Does this help?

Last edited: Jan 27, 2008