Write the equations of motion of a pendulum consisting of a thin, 4 kg stick of length l suspended from a pivot. How long should the rod be in order for the period to be exactly 2 sec? (The inertia l of a thin stick about an end point is 1/3 ml2. Assume that θ is small enough that sin θ ≅ = θ.) Why do you think grandfather clocks are typically about 6 ft high?