Which of the following assumptions are required to conduct an experiment to accomplish the goal of measuring Young's modulus?
The change in cross-sectional area that occurs when stress is applied can be safely neglected in calculating
Young's modulus.
The material is uniform; in other words, the strain of one part of it is the same as the strain in another part
when the same stress is applied.
The material is elastic; it is returning to its original length (and thickness) when the stress is no longer
applied.
Friction is negligible at the point where the stress is being applied to the material.
The mass of the material is much less than the mass of the ring stand.
The force is being applied uniformly across the cross-sectional area of the material being stretched.

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.