A potential difference V0 is applied, with a battery, to the plates of a parallel-plate capacitor of plate-area A and separation d. Write an expression for each of the
following:
(a) the capacitance C0 of the capacitor,
(b) the free charge q0,
(c) the electric field strength E0 in the gap.
Now the battery is disconnected and a dielectric slab of thickness b and dielectric
constant κ is inserted in the gap.
(d) What happens to the free charge?
(e) What happens to the field strength in the gap?
(f) What is the field strength in the dielectric slab?
(g) Find an expression for the potential difference between the two plates.
(h) Find an expression for the capacitance C now.
(i) Assume that C becomes double of C0 when a slab of dielectric constant 10 is
inserted. What is the thickness b?

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

where is unknown. because the position is parabolic, there is symmetry about the midpoint at , and we know that

so that the position function is

which means the velocity is

then the total distance traveled is

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at and ends at , so its displacement is 0.