The age of the father 4 years ago was 8 times the age of his son. At present, the father's age is 4 times that of his son. Find the present age of son.
Amish Tripathi, a famous Indian writer, is working on a series based on Ramayana, in which the first two books focus on Rama and Sita, respectively. On which character does the third book of this series focus?
Two particles with charges q1 and q2 are kept at a certain distance to exert force F on each other. If the distance is reduced to one-fifth, then the force between them is