phy (electrostatics)

The electrostatic force F between the two charged particles is given by Coulomb's Law,F = k(Q1).(Q2)/r^2where k is a constant
Q1 and Q2 are the charges respectively on the particles
r is their distance of separation

Since the two charges are both positive, the force is repulsive.
acceleration a = F/m, where m is the mass of each particle.

thus, a = k(Q1).(Q2)/m(r^2)
It is thus clear that because of the repulsive force, the two particles will be moving away from one another. In doing so, r increases with time, and hence a decreases with time.

因為佢地都係 +ve charge, 即係佢地係like charges，佢地released 咗之後，就會repel, 走相反方向。最初acceleration 會大D, 因為佢地distance 較近，當他們一直 repel, distance就長咗，影響大家的程度少咗，repel 的程度就會細咗，所以acceleration 都會細咗，所以就decrease with time。