Search results for query: *

I am mainly looking for some modern book with media links in the book.

so you can't recommend to your students any English books?

If you are a high-school teacher can't you recommend a few books?

Is there a good "classic" book available?

Can you recommend introductory physics book for high school that contains E & M ? It should not have any integrals.

1 - cos^2(10) + sin^2(10) = 2sin^10 because cos^2(10) + sin^2(10) = 1

I have checked this and I get r = 2a*sin10

I don't think I will need these advance techniques in my exercises

sqrt(4a^2sin^2(10)) = 2*a*sin10 How do you get from 1 - cos^2(10) - sin^2(10) to 2 sin^2(10) ?

I still don't see how this is correct as angle 10 is not adjacent to r

correct solution

It looks like the Tan approach was correct

When I changed the sign now result looks correct. I don't think you can get r in such a way because angle 10 degrees is not adjacent to r

This looks easy, but why was my attempt flawed with Tan10 ?

q*q/(4*PI*Eps0*r^2) = (m*g / Cos10) * Sin10 And then just move everything except q on the right side

Into the bottom equitation I can insert equation for T and get q which is the only unknown?

T = mg / Cos10 Fx = Fe = T*sin10

Fx/T = sin 10 -> Fx = Fe = T*sin10

this Fx - Fe = 0 Fx = (1/(4*PI*Eps0))*(q*q/r^2)

that is cosinus -> T = mg / Cos10

I can paste the text in my native language but I don't know if it would help

Fe = Fx Fg = Fy Fx = (1/(4*PI*Eps0))*(q*q/r^2) Fy = mg

horizontal: Fx - Fe = 0 -> Fe = Fx vertical: Fg - Fy = 0 -> Fg = Fy

ok but neither the Tension nor Fe are known, and we need Fe ?

If you want to use Pythagorean theorem or Cos/Sin function you need one angle to be 90 degrees.

I have used for gamma = 60 and got correct result but how do you know that gamma = 60 ? I don't know why I thought that any of the angles is 90 degrees. The correct result:

Should I use the Law of cosines ? c^{2}=a^{2}+b^{2}-2ab*cos Then I would need angle gamma? I have updated the picture

I have used Cosines to calculate Fr and I still don't get the correct result:

I am satisfied with easier route for this exercise.

That is a very strange exercise with a lot of redundant information it seems

Do I need to determine it to solve this exercise?

but where is the electrical force and what about all the rest of information (mass, charge, distance)

You mean like that? Fthread = Fceiling + Fbody = 0

aha I understand that, but what is then acting on the threads?

2 Electrical forces and 2 gravitational forces

yes but we need to know the sum of all forces on all threads

what is it asking ?

As you said there are 2 threads : Fthread1 = Fg - Fe //upper thread Fthread2 = - Fg - Fe

I will check if forces are right-angled

gravitational and electrical force

I would say this is correct: Fthread = -Fg1 - Fg2 - Fe1 + Fe2 so 2 gravitational forces point down and 1 electrical force is pointing up

I think that this is correct? Fthread = -Fg1 - Fg2 - Fe1 + Fe2

As I understand the exercise there are 2 forces acting on these thread, gravitational and electrical. And the sum of both is suppose to be 0.

Something like that? Fthread = Fg1 + Fg2 + Fe1 + Fe2

I mean all the forces working on the thread combined. A sum of all the forces working on that thread. Which are only force of gravity and electrical force. And the sum of all those forces working on a thread should be 0. I have provided all the information from the book. I have translated the...

F23 is a force on the 3rd charge from 2nd charge F13 is a force on the 3rd charge from the 1st charge Fr is a sum of both (Pythagorean theorem).

If the balls have both the same mass and charge They are both charged with the same charge as I already specified. No information about if they are the same weight. Assume they are both the same weight. Which thread tension you wish to found. The combine force in the thread.