When an object such as a plastic comb is charged by rubbing it with a cloth, the net charge is typically a few microcoulombs. if that charge is 4.0 ? c , by what percentage does the mass of a 33 g comb change during charging?

The concept required to solve this problem is quantization of charge.

First the number of electrons will be calculated and then the total mass of the charge.

With these data it will be possible to calculate the percentage of load in the mass.

Here Q is the charge, n is the number of electrons and e is the charge on the electron

Replacing,

According to the quantization of charge the charge is defined as product of the number of electron and the charge on the electron

The total mass of the charge is

Here,

m = Mass of the charge

n = Number of electrons

= Mass of the electron

Replacing we have

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.