A small 1.00-g plastic ball that has a charge $q$ of $1.00$ C is suspended by a string that has a length $L$ of $1.00 \mathrm{~m}$ in a uniform electric field, as shown in Figure 16-30. If the ball is in equilibrium when the string makes a $9.80^{\circ}$ angle with the vertical as indicated by $\theta$, what is the electric field strength? Example 16-5