4.2 a beta-emitting radioactive isotope called iodine-131 is often released into the air during nuclear
accidents. it can settle on skin and clothing and can be inhaled or ingested. iodine is absorbed in
the body by the thyroid gland, where it is used to make molecules that travel throughout the body.
when the thyroid gland has enough iodine, any excess iodine is removed by the body. if a nuclear
accident occurs at a power plant, workers are asked to ingest potassium iodide tablets which
contain a stable isotope of iodine. explain how this minimises the risk of damage to their bodies.

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.

the components of a vector are the parts of the vectors that are to each other.

b perpendicular