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## Homework Statement

A charged ball of mass 0.2[gr] and q=6E-9[Coulomb] hangs on a string between 2 plates that are 5[cm] apart. the ball makes 30

^{0}with the vertical. what is the voltage difference of the plates.

## Homework Equations

Electric field: $$E[\frac{N}{Coulomb}]=\frac{V}{S[m]}$$

The force: $$F=E\cdot q$$

## The Attempt at a Solution

The horizontal force: $$F_x=mg\cdot \tan 30^0=2E-4[Kg]\cdot 10\cdot \tan 30^0=11E-6[N]$$

The field: $$11E-6[N]=E\cdot 6E-9[Coulomb]\rightarrow E=1924.5[V]$$

Seems small.

##E=\frac{V}{0.05[m]}\rightarrow 1924.5=\frac{V}{0.05[m]} \rightarrow V=96[V]##

It should be 9440[V]