Work Power Energy question bank (Physics)

A particle is whirled in a vertical circle of radius $R$. If its velocity at the lowest point is just enough to complete the circle ($u = \sqrt{5gR}$), then the magnitude of its total acceleration when the string becomes horizontal is ($g$ is acceleration due to gravity).

A simple pendulum oscillates with an angular amplitude $\theta$. If the maximum tension in the string is 4 times the minimum tension then the value of $\theta$ is