I am not able think of convincing answers to the following questions- 1.Why the distance between knife edges (when the time periods about them is approx same) is considered equal to the length of an equivalent simple pendulum ?? It will be great if you can derive it.... 2. Why the ends of the rod of Kater's pendulum are sharpened (pointed) ?? 3. Why the rod itself is so heavy ? I don't have a clue to question 1's answer.... For question 2, I think it is only so that we can better see when the pendulum passes a certain reference point, thus reducing the error in measurement of time period....but this is not satisfying because a bar pendulum does not have such ends (the rod in bar pendulum is cylindrical with flat ends).... For question 3, I think it is to reduce the effect of buoyancy due to air ?? I am not sure... Any help will be appreciated.