# Physics II: Determine Electric Field Intensity for Equilibrium

In summary, two 3.0 g spheres with charges of -4.X10-8 C and +4.X10-8 C are suspended by light strings of 9.0 cm in length. To achieve equilibrium at θ = 11°, a uniform electric field intensity needs to be determined. To solve this problem, one must consider the forces on each charge, sketch their vectors on a diagram, and write equations stating that the sum of the forces in the horizontal and vertical directions are zero. This can be done by setting F = ma = 0. By organizing the numbers and using appropriate equations, the electric field intensity can be calculated in units of Newtons/Coulomb.

## Homework Statement

Two 3.0 g spheres are suspended by 9.0 cm long light strings. A uniform electric field is applied in the x direction. If the spheres have charges of -4.X10-8 C(coulomb) and +4.X10-8 C, determine the electric field intensity that enables the spheres to be in equilibrium at θ = 11°.

picture: http://www.webassign.net/sercp/p15-57.gif

So the units to the answer should be Newtons/Coulomb

## The Attempt at a Solution

I am unclear on how to get the answer because i feel overwhelmed by formulas I can use. I've tried and the answer is definitely not 304,843.5. You see what I mean?

I would appreciate some ideas.

-Abe

Consider the forces on each charge. Sketch their vectors on a diagram. Write equations saying that the sum of the forces on each charge in the horizontal and vertical directions are zero (because they are not accelerating, F = ma = 0).

Delphi51 said:
Consider the forces on each charge. Sketch their vectors on a diagram. Write equations saying that the sum of the forces on each charge in the horizontal and vertical directions are zero (because they are not accelerating, F = ma = 0).

Could you tell me how do i organize the number to get the answer? as in what equations do I use as well.