Chapter 22, Problem 60P

A certain electric dipole is placed in a uniform electric field $\stackrel{\to }{E}$ of magnitude 40 N/C. Figure 22-63 gives the magnitude τ of the torque on the dipole versus the angle θ between field $\stackrel{\to }{E}$ and the dipole moment $\stackrel{\to }{p}$. The vertical axis scale is set by τ_s = 100 × 10^-28 N · m. What is the magnitude of $\stackrel{\to }{p}$?

Figure 22-63 Problem 60.