Physics problem

[bleak sandal]

Can somebody guide me through the solution of this problem

[real needle]

Are there any options??

Also post ur work

#rules

For solution u can start by equating the forces

[royal fjord]

I think that what they expect is gravitational force (which is downwards) is equal to electrostatic repulsive force (which is upwards) (thereby satisfying newton's first and second laws) and all you need to do is find the gravitational force (mg) and equate it to electrostatic force (kQq/r^2), set the charge of A to be q, which is given, and solve for Q, which is the value of the positive charge and seems to be the condition you need to identify, with r being the height.

symbolically it is

$Q = \frac{mgr^2}{kq}$

[hoary marten]

Chiara

[royal fjord]

k is coulomb's constant

$k=\frac{1}{4\pi\epsilon_0}$

[hoary marten]

Chiara

[royal fjord]

$\epsilon_0 = 8.85 \cdot 10^{-12} Fm^{-1}$

[hoary marten]

Chiara

[royal fjord]

$g = 9.81 \space ms^{-2}$

[hoary marten]

Chiara

[bleak sandal]

Should i assume height, r = 20m?

[royal fjord]

yes

[royal fjord]

id be a bit more accurate and use this

but

seems fine to me

[bleak sandal]

So the condition is that the positive charge on the ground has to have 6.22 x 10^-3 coulomb charge?

[royal fjord]

that is how i understood it yes

[bleak sandal]

Thank u !!

[royal fjord]

np

[bleak sandal]

Could u help me with this too?

Dw if u're not free

[royal fjord]

okay so first thing is to recognize that the charges at A and C are equal and M is the midpoint, therefore the electric field due to charges A and C at M is zero

which would imply that there is field due to charge B

then you find the distance between B and M (geometry)

and use

$E = \frac{kq}{r^2}$

[hoary marten]

Chiara

[royal fjord]

OH one important thing before doing any of this, convert the centimeters to meters and the microcoulombs to coulombs

use SI units

else ur gonna get a power of 10 error

[bleak sandal]

I hope i got the right answer