Answer:
Area under a curve can be estimated via block counting, calculated with simple geometry if the velocity has constant accelerations, or calculated by integration if the velocity can be described by a mathematical equations.
The area under a velocity time curve will be the product of velocity and time which equals displacement.
(a) Force between the two charges
The electrostatic force between the two charges is given by:
where k is the Coulomb's constant, q1 and q2 the two charges, r their separation.
In this problem:
Substituting into the equation, we find
(b) direction of particle q2
Particle q2 wants to move in the direction of the force acting on it. The direction of the force depends on the relative sign of the two charges: like charges attract each other, opposite charges repel each other. In this case, the two charges are both positive, so they repel each other and q2 tends to move away from particle q1.