Answer:
Q = 6.33μC
Explanation:
To find the value of the charge Q you take into account both gravitational force and electric force over each ball. By symmetry you can use the fact that both balls experiences the same forces. Hence you only take into account the forces for one ball for the x component and y component:

M: mass of the ball = 0.09kg
T: tension of the string
F_e: electric force between charges
angle = 45°
The electric force is given by:

Q: charge of the balls
r: distance between balls = 2m
You divide both equation in order to eliminate the tension T:

By doing Q the subject of the formula and replacing you obtain:

hence, the charge of the balls is 6.33μC
Answer:
D
Explanation:
this is simple, because when air is removed, means that there is no particles in the jar so vacuum is achieved, and when you can't hear a sound means that the sound couldn't travel through the vacuum. which means that sound cannot travel through vacuum,
as a result, sound requires a medium ( air) travel from one point to another.
hope it helps, if not please report it so that someone else gets to try it
Look at your speedometer for say, a couple of seconds. Depends on whether or not you are moving on average at a constant speed (speedo won't change much) or whether you're in a polluting traffic jam/queue in which case the speedo will go up and down like a yo yo. to determine the speed, you'd probably need to plot the speed on the speedo against the times at which the speedo speeds were read from the speedo.
Force, F = ma
Where m = mass in kg, a = acceleration in m/s², Force, F is in N.
F = ma
2000 = m*2.2
2.2m = 2000
m = 2000/2.2
m ≈ 909.09
Mass is ≈ 909.09 kg.