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Homework Statement
An electric dipole consists of 1.0 g spheres charged to +(-) 2.0 nC at the ends of a 10-cm-long massless rod. The dipole rotates on a frictionless pivot at it's center. The dipole is held perpendicular to a uniform electric field with field strength 1000 V/m, then released. What is the dipoles angular velocity at the instant it is aligned with the electric field?
Homework Equations
E= ΔVc/d
U = (Kq1q2)/r
qΔv = Kf + qΔV
ω = dθ/dt
The Attempt at a Solution
book answer = .28 rad/sec
I am at a loss as to where to start on this solution. The object shouldn't have any kinetic initial because it is motionless. I am supposed to calculate angular velocity after it passes 90°, yet do I use energy? I have tried using the following
U(int) = Kfinal + Ufinal
Kq1q2-r = kq1q2 + .5Iω^2
However, as you can see the Potentials cancel out to zero and give me a zero answer. There is an obvious flaw in my reasoning. Can someone please lead me in the right direction? Thanks.