Question

A pendulum oscillates in a vertical plane, length of string is 1m. At what point vertically below the point of suspension must a nail be fixed so that bob starts revoluting about the nail as its centre?
Pendulum makes 60degree with the vertical.
Pl.answer with explanation

Answer 1

are u asking for the point where there is maximum oscilaton of the pendulum when the nail is fixed?

Answer 2

initial potential energy of bob = mg(1/2) = kinetic energy at lowest point = (1/2)mv^2
frm here v = \[\sqrt{10}\]
now to complete a circle a speed to \[\sqrt{5gx}\] (radius of circle) is required..
\[\sqrt{5gx}\] = \[\sqrt{10}\]
=> x = 0.2 (from lowest point).