When an old building is to be torn down, Mr. Pham’s company removes the bricks, cleans off the mortar from the bricks, and then sells the bricks to companies that restore historic buildings. Which compound is Mr. Pham’s company most likely to use in its work? hydrochloric acid
nitric acid
sodium hydroxide
lithium hydroxide

hydrochloric acid

Explanation:

The compound Mr. Pham's company used is most likely hydrochloric acid.

Hydrochloric acid is a strong acid and it is applied to remove corrosion and rusts from another body.

The acid is capable of dissolving and breaking down the rust and corrosion.

A base does not have this property and would not effectively remove the corrosion.

Sodium hydroxide and lithium hydroxide are bases.

Nitric acid is not as strong as hydrochloric acid.  

layers of the earth affect the waves and these effects are seen on instruiments such as seimometers

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.