What about the component of Newton's Law in the radial direction?
Recall that the bob doesn't move in the radial direction. This means that the tension T in the rod must balance
the radial component of the force due to gravity and the radial acceleration of the mass. Use Newton's Second Law

in terms of
,
m, and g in the little quiz below. Recall the figures on the
Undamped Math Model Concepts page.
What is Fr?
It can be shown that the radial acceleration is given by

Now substitute these expressions for
and
into the equation
and solve for T.
What is the tension in the rod?