Sir william herschel counted the number of stars in different directions, and getting similar numbers in each direction along the disk, concluded the sun was near the center of a disk like collection of stars. herschel came to the wrong conclusion about the sun's location because(a) he was predisposed to believe the sun is the center of the milky way, and ignored the data which disagreed with that conclusion. (b) he did not know that interstellar dust made it hard from him to see a large part of the milky way's disk. (c) he only counted globular cluster, and not regular stars. (d) the sun's position in the milky way at that particular time was very unusual and skewed in his results.

the correct answer is (B) He did not know that interstellar dust made it hard from him to see a large part of the Milky Way's disk.

Explanation:

We live in a dusty Galaxy. Because interstellar dust absorbs the light from stars, Herschel could see only those stars within about 6000 light-years of the Sun.

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.