Electric Charge/Gravitational Pull

[KTiaam]

Homework Statement

So in class we are learning about electric charge and we were shown a video of a small ball being attracted to a larger ball by an electric charge. We are given some data about the balls below. There are two questions associated with this problem.

(we are trying to prove that the force shown from the video was to large to be a graviational pull, and thus it is a electrical force)
1.
Calculate the attractive gravitational force that the spheres exert on one another.
2.
Calculate the actual force that is being exerted on the small ball by the large ball to pull it away from vertical by the angle shown in the diagram.
(diagram is just a small ball on rope being attracted to a bigger ball)

Homework Equations

Mass of Big ball = 150g
Radius of Big ball = 10.0cm

Mass of Small ball = 0.05 g
Radius of Small ball = 0.5cm

The Attempt at a Solution

I know how to do the first problem, what I am having problem is understanding the second problem. There is no force besides electronic force acting on it, correct? What equation do i use.

please help me in the correct direction.
any help is greatly appreciated.

 

[haruspex]

There is no force besides electronic force acting on it, correct? What equation do i use.

If that were the only force the small ball would accelerate until it hit the larger ball. What stops it?
(Btw, it's an electric force, not an electronic one.)

 

[KTiaam]

If that were the only force the small ball would accelerate until it hit the larger ball. What stops it?
(Btw, it's an electric force, not an electronic one.)

tension due to the string?

 

[haruspex]

tension due to the string?

Yes, and there's a third force. Draw the free body diagram, with the ball pulled a little towards the larger ball by the electric field, so that the string is not vertical. What equations can you write down?

 

[KTiaam]

Yes, and there's a third force. Draw the free body diagram, with the ball pulled a little towards the larger ball by the electric field, so that the string is not vertical. What equations can you write down?

tension and gravity

 

[haruspex]

tension and gravity

So you have the three forces. What about the equations (∑F=0)?