Two particles, with identical positive charges and a separation of 2.12 × 10-2 m, are released from rest. immediately after the release, particle 1 has an acceleration a1 whose magnitude is 3.64 × 103 m/s2, while particle 2 has an acceleration a2 whose magnitude is 8.47 × 103 m/s2. particle 1 has a mass of 4.60 × 10-6 kg. find (a) the charge on each particle and (b) the mass of particle 2.

1) Particle 1 has an acceleration of , and this acceleration is caused by the electric force between the two particles, F.
For Newton's second law:

and using the mass of particle 1, we find the magnitude of the electric force:


The electric force is also given by:

where 
is the Coulomb's constant
is the charge of the two particles (they are identical, so they have same charge)
is the initial distance between the two particles.
Using the value of the force we found previously, and by re-arranging this formula, we can calculate the value of q, the charge of each particle:


(b) We can calculate the mass of particle 2 by applying Newton's second law:

where F is again the electric force. So, we find