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**1. Homework Statement**

A water molecule is a permanent dipole with a dipole moment p = qs. There is a water molecule in the air a very short distance x from the midpoint of a long rod of length L and uniform charge +Q. The axis of the rod is perpendicular to the rod. Note that s << x << L.

a) Find the the force of the rod on the molecule in terms of Q, L, x, p.

b) If the electric field on the molecule when it is 1 cm from the rod is 10^6 N/C and p = 6*10^-30 and the mass of the molecule is m. What is the acceleration of the molecule?

**2. Homework Equations**

F = ma For a rod: F = k(Q/r*sqrt(r^2 + (L/2)^2)), k = 9*10^9

F = qE

**3. The Attempt at a Solution**

I have done a and get:

Force of rod on molecule: F = 2kQp/Lx^2

(toward the rod and perpendicular to it)

My problem is that I'm not sure how to get b. I don't know how to eliminate using given data, Q and L. Please help. Thank you.