A simple pendulum of length ξ and mass m is suspended from a point on the circumference of a thin massless disc of radius α that rotates with a constant angular velocity ω about its central axis as shown in Figure. Find the equation of motion of the mass m.
L = T - V
The Attempt at a Solution
Firstly, I know I should find its x' and y' which representing its velocity.
i.e. T - V = 1/2 m ( x_dot 2 + y_dot 2 ) - mgy
However, I don't know where I should start with to find their x and y.