A proton is kept at rest. A positively charged particle is released from rest at a distance d in its field. Consider two experiments; one in which the charged particle is also a proton and in another, a positron. In the same time t, the work done on the two moving charged particles is
1
same as the same force law is involved in the two experiments.
2
less for the case of a positron, as the positron moves away more rapidly and the force on it weakens.
3
more for the case of a positron, as the positron moves away a larger distance.
4
same as the work done by charged particle on the stationary proton.